Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Feb. 12, 2019	Jun. 30, 2018
Document and Entity Information [Line Items]
Entity Registrant Name	APPIAN CORP
Entity Central Index Key	0001441683
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Trading Symbol	APPN
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Class A Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		30,447,805
Entity Public Float			$ 696,466,225
Class B Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		33,807,128
Entity Public Float			$ 119,394,534

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 94,930	$ 73,758
Accounts receivable, net of allowance of $600 and $400 at December 31, 2018 and 2017, respectively	79,383	55,315
Deferred commissions, current	14,020	9,117
Prepaid expenses and other current assets	21,293	7,032
Total current assets	209,626	145,222
Property and equipment, net	7,539	2,663
Deferred commissions, net of current portion	15,088	12,376
Deferred tax assets	326	281
Other assets	601	510
Total assets	233,180	161,052
Current liabilities
Accounts payable	9,249	5,226
Accrued expenses	7,464	6,467
Accrued compensation and related benefits	13,796	12,075
Deferred revenue, current	95,523	70,165
Other current liabilities	2,369	1,182
Total current liabilities	128,401	95,115
Deferred tax liabilities	42	87
Deferred revenue, net of current portion	16,145	18,922
Deferred rent, net of current portion	15,400	1,404
Total liabilities	159,988	115,528
Stockholders’ equity
Additional paid-in capital	218,284	141,268
Accumulated other comprehensive income	542	439
Accumulated deficit	(145,640)	(96,189)
Total stockholders’ equity	73,192	45,524
Total liabilities and stockholders’ equity	233,180	161,052
Class A Common Stock
Stockholders’ equity
Common stock	3	1
Class B Common Stock
Stockholders’ equity
Common stock	$ 3	$ 5

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 600	$ 400
Common stock, par value (in usd per share)	$ 0.0001
Class A Common Stock
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	29,626,054	13,030,081
Common stock, shares outstanding (in shares)	29,626,054	13,030,081
Class B Common Stock
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	34,290,383	47,569,796
Common stock, shares outstanding (in shares)	34,290,383	47,569,796

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Total revenue	$ 60,216	$ 54,948	$ 59,883	$ 51,696	$ 50,562	$ 44,648	$ 43,198	$ 38,329	$ 226,743	$ 176,737	$ 132,923
Cost of revenue:
Total cost of revenue	22,210	20,092	21,574	21,049	18,657	16,613	16,637	12,690	84,925	64,597	50,123
Gross profit	38,006	34,856	38,309	30,647	31,905	28,035	26,561	25,639	141,818	112,140	82,800
Operating expenses:
Sales and marketing	30,177	25,467	27,384	22,964	22,463	19,725	22,775	17,003	105,992	81,966	54,137
Research and development	12,332	11,737	10,785	9,870	8,968	8,596	9,971	7,300	44,724	34,835	22,994
General and administrative	8,799	12,537	8,425	8,060	7,429	6,237	8,635	4,849	37,821	27,150	17,039
Total operating expenses	51,308	49,741	46,594	40,894	38,860	34,558	41,381	29,152	188,537	143,951	94,170
Operating loss	(13,302)	(14,885)	(8,285)	(10,247)	(6,955)	(6,523)	(14,820)	(3,513)	(46,719)	(31,811)	(11,370)
Other expense (income):
Other expense (income), net	510	110	2,593	(918)	(380)	(425)	(734)	(499)	2,295	(2,038)	1,792
Interest expense	64	67	54	13	22	(2)	197	256	198	473	982
Total other expense (income)	574	177	2,647	(905)	(358)	(427)	(537)	(243)	2,493	(1,565)	2,774
Loss before income taxes	(13,876)	(15,062)	(10,932)	(9,342)	(6,597)	(6,096)	(14,283)	(3,270)	(49,212)	(30,246)	(14,144)
Income tax expense (benefit)	27	(34)	35	211	272	188	176	125	239	761	(1,683)
Net loss	(13,903)	(15,028)	(10,967)	(9,553)	(6,869)	(6,284)	(14,459)	(3,395)	(49,451)	(31,007)	(12,461)
Accretion of dividends on convertible preferred stock									0	357	857
Net loss attributable to common stockholders									$ (49,451)	$ (31,364)	$ (13,318)
Net loss per share attributable to common stockholders:
Basic and diluted (in dollar per share)									$ (0.80)	$ (0.63)	$ (0.39)
Weighted average common shares outstanding:
Basic and diluted (in shares)									62,140,684	49,529,833	34,274,718
Subscriptions, software and support
Revenue:
Total revenue	35,108	30,905	33,047	26,952	25,398	22,660	22,012	21,444	$ 126,012	$ 91,514	$ 69,972
Cost of revenue:
Total cost of revenue	3,284	3,261	2,824	2,628	2,488	2,341	2,488	2,062	11,997	9,379	7,437
Professional services
Revenue:
Total revenue	25,108	24,043	26,836	24,744	25,164	21,988	21,186	16,885	100,731	85,223	62,951
Cost of revenue:
Total cost of revenue	$ 18,926	$ 16,831	$ 18,750	$ 18,421	$ 16,169	$ 14,272	$ 14,149	$ 10,628	$ 72,928	$ 55,218	$ 42,686

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (49,451)	$ (31,007)	$ (12,461)
Comprehensive loss, net of income taxes:
Foreign currency translation adjustment	103	(891)	359
Total other comprehensive loss, net of income taxes	$ (49,348)	$ (31,898)	$ (12,102)

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Restricted stock units	Restricted stock units Common Stock
Beginning balance (in shares) at Dec. 31, 2015		34,274,718
Beginning balance at Dec. 31, 2015	$ (50,533)	$ 3		$ 971	$ (51,507)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(12,461)				(12,461)
Accretion of dividends on convertible preferred stock	(857)				(857)
Other comprehensive loss	359			359
Ending balance (in shares) at Dec. 31, 2016		34,274,718
Ending balance at Dec. 31, 2016	(63,492)	$ 3		1,330	(64,825)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(31,007)				(31,007)
Accretion of dividends on convertible preferred stock	(357)				(357)
Conversion of convertible preferred stock to common stock (in shares)		18,163,158
Conversion of convertible preferred stock to common stock	48,207	$ 2	$ 48,205
Conversion of convertible preferred stock warrant to common stock warrant	1,191		1,191
Issuance of common stock from initial public offering, net of issuance costs (in shares)		7,187,500
Issuance of common stock from initial public offering, net of issuance costs	$ 77,789	$ 1	77,788
Exercise of common stock warrant (in shares)		79,363
Issuance of common stock to directors (in shares)		14,087
Vesting of restricted stock units (in shares)						4,930	4,930
Exercise of stock options (in shares)	876,121	876,121
Exercise of stock options	$ 1,108		1,108
Stock-based compensation expense	12,976		12,976
Other comprehensive loss	(891)			(891)
Ending balance (in shares) at Dec. 31, 2017		60,599,877
Ending balance at Dec. 31, 2017	45,524	$ 6	141,268	439	(96,189)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(49,451)				(49,451)
Issuance of common stock from initial public offering, net of issuance costs (in shares)		1,675,000
Issuance of common stock from initial public offering, net of issuance costs	$ 57,829		57,829
Issuance of common stock to directors (in shares)		11,952
Vesting of restricted stock units (in shares)						143,390	143,390
Exercise of stock options (in shares)	1,486,218	1,486,218
Exercise of stock options	$ 3,133		3,133
Stock-based compensation expense	16,054		16,054
Other comprehensive loss	103			103
Ending balance (in shares) at Dec. 31, 2018		63,916,437
Ending balance at Dec. 31, 2018	$ 73,192	$ 6	$ 218,284	$ 542	$ (145,640)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (49,451)	$ (31,007)	$ (12,461)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization	2,021	886	764
Gain on disposal of equipment	(4)	0	0
Bad debt expense	211	62	7
Deferred income taxes	(218)	(251)	(1,122)
Stock-based compensation	16,054	12,976
Fair value adjustment for warrant liability	0	341	200
Loss on extinguishment of debt	0	384	0
Changes in assets and liabilities:
Accounts receivable	(23,332)	(9,716)	(11,154)
Prepaid expenses and other assets	(1,025)	(4,162)	(1,665)
Deferred commissions	(7,615)	(3,487)	(5,335)
Accounts payable and accrued expenses	7,461	4,128	1,287
Accrued compensation and related benefits	(3)	2,365	3,717
Other current liabilities	1,823	383	19
Deferred revenue	23,023	18,344	17,410
Deferred rent, non-current	(266)	(374)	577
Net cash used in operating activities	(31,321)	(9,128)	(7,756)
Cash flows from investing activities:
Purchases of property and equipment	(7,014)	(433)	(984)
Proceeds from sale of equipment	4	0	0
Net cash used in investing activities	(7,010)	(433)	(984)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting discounts	0	80,213	0
Proceeds from public offering, net of underwriting discounts	58,258	0	0
Payment of costs related to public offerings	(429)	(2,424)	0
Payment of dividend to Series A preferred stockholders	0	(7,565)	0
Proceeds from exercise of common stock options	3,133	1,108	0
Proceeds from issuance of long-term debt, net of debt issuance costs	0	19,616	20,000
Repayment of long-term debt	0	(40,000)	(10,000)
Net cash provided by financing activities	60,962	50,948	10,000
Effect of foreign exchange rate changes on cash and cash equivalents	(1,459)	1,228	(1,510)
Net increase (decrease) in cash and cash equivalents	21,172	42,615	(250)
Cash and cash equivalents, beginning of period	73,758	31,143	31,393
Cash and cash equivalents, end of period	94,930	73,758	31,143
Supplemental disclosure of cash flow information:
Cash paid for interest	46	515	895
Cash paid for income taxes	680	615	610
Supplemental disclosure of non-cash financing activities:
Accretion of dividends on convertible preferred stock	0	357	857
Conversion of Convertible Preferred Stock to Common Stock
Supplemental disclosure of non-cash financing activities:
Conversion of convertible stock	0	48,207	0
Conversion of Convertible Preferred Stock Warrant to Common Stock Warrant
Supplemental disclosure of non-cash financing activities:
Conversion of convertible stock	$ 0	$ 1,191	$ 0

Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements and footnotes have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) as contained in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (the “Codification” or “ASC”).

Use of Estimates

The preparation of our consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and judgments that affect the amounts reported in these consolidated financial statements and accompanying notes. Although we believe that the estimates we use are reasonable, due to the inherent uncertainty involved in making these estimates, actual results reported in future periods could differ from those estimates.

Significant estimates embedded in the consolidated financial statements include revenue recognition, income taxes and the related valuation allowance, stock-based compensation and fair value measurements for our common stock and preferred stock warrant.

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of Appian and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Initial Public Offering

In May 2017, we completed an initial public offering ("IPO"), in which we sold 7,187,500 shares of our newly-authorized Class A common stock at an initial price to the public of $12.00 per share. We received net proceeds of $77.8 million, after deducting underwriting discounts and commissions and offering expenses paid and payable by us, from the IPO.

Deferred offering costs of $2.4 million, consisting of legal, accounting and other fees and costs related to our IPO, were recorded to additional paid-in capital as a reduction of the proceeds upon the closing of our IPO.

Secondary Offering

In November 2017, we completed a secondary offering in which stockholders sold an aggregate of 4,370,000 shares of our Class A common stock at a price of $20.25 per share. We did not receive any proceeds from the sale of the shares of our Class A common stock sold in the secondary offering.

Public Offering

In August 2018, we completed an underwritten public offering of 2,000,000 shares of our Class A common stock, of which 1,675,000 shares of Class A common stock were sold by us and 325,000 shares of Class A common stock were sold by existing stockholders, at on offering price to the public of $35.15 per share. Our net proceeds from the offering were $57.8 million, after deducting underwriting discounts and commissions and offering expenses. We did not receive any of the proceeds from the sale of shares by the selling stockholders.

Revenue Recognition

We generate revenue primarily through sales of subscriptions to our platform, as well as professional services. To a lesser extent, we also generate revenue from the sale of perpetual software license agreements and associated maintenance and support. We recognize revenue when all of the following conditions are met: (1) there is persuasive evidence of an arrangement; (2) the service or product has been provided to the customer; (3) the amount of fees to be paid by the customer is fixed or determinable; and (4) the collection of related fees is reasonably assured. If collection is not reasonably assured, we defer revenue recognition until collectability becomes reasonably assured. Our arrangements do not contain rights of return. Revenue is recognized net of any taxes collected from customers and subsequently remitted to governmental authorities.

Subscriptions, Software and Support Revenue

Subscriptions, software and support revenue is primarily related to (1) software as a service (“SaaS”) subscriptions bundled with maintenance and support and hosting services and (2) term license subscriptions bundled with maintenance and support. To a lesser extent, we also generate revenue from the sale of perpetual software licenses and associated maintenance and support.

Historically, we licensed our software primarily under perpetual licenses, but over time we transitioned from perpetual licenses to subscriptions. Revenue from our perpetual software licenses was 2.0% of our total revenue for 2018. Revenue from our perpetual software licenses was less than 1.0% of our total revenue for each of 2017 and 2016.

We generally charge subscription fees on a per-user basis and, to a lesser degree, non-user based single application licenses. We bill customers and collect payment for subscriptions to our platform in advance on a monthly, quarterly or annual basis. In certain instances, we have had customers pay their entire contract up front.

SaaS Subscriptions

Our SaaS subscription revenue is derived from customers accessing our cloud offering pursuant to contracts that are generally one to five years in length. We perform all required maintenance and support for our cloud offering and we do not separately charge customers for hosting costs. In these arrangements, our customers do not have the right to take the software on-premises and, as a result, such arrangements are not accounted for within the scope of the software revenue guidance. Revenue from SaaS subscriptions is recognized ratably over the term of the subscription, beginning with the date our service is made available to our customer.

Term License Subscriptions

Our term license subscription revenue is derived from customers with on-premises installations of our platform pursuant to contracts that are generally one to five years in length. Customers with term license subscriptions have the right to use our software and receive maintenance and support. Since we do not sell maintenance and support separately from the subscription, revenue for the term license subscription and maintenance and support is recognized ratably over the term of the subscription, upon delivery of the platform to the customer when sold on a standalone basis.

Perpetual Licenses

Our perpetual license revenue is derived from customers with perpetual licenses to our platform and associated maintenance and support contracts. We recognize revenue from perpetual licenses on the date of delivery to our customer. We sell maintenance and support to perpetual license customers separately from the perpetual licenses pursuant to agreements that generally renew annually. Maintenance and support revenue is deferred and recognized ratably over the term of the support period.

Professional Services

Our professional services revenue is comprised of fees for consulting services, including application development and deployment assistance and training related to our platform. Our professional services are not essential to the functionality of our platform because the platform is ready for the customer’s use immediately upon delivery and is not modified or customized in any manner.

Consulting services are billed under both time-and-material and fixed-fee arrangements. For standalone time-and-material contracts, we recognize revenue at contractually agreed upon billing rates applied to hours performed. For standalone fixed-fee contracts, we also recognize revenue as the work is performed using the proportional performance method of accounting. Training revenue is recognized when the associated training services are delivered. Training is also sold in the form of a subscription arrangement where a customer agrees to pay an annual fixed fee for a fixed number of users to have access to all of our training offerings during the year. Revenue from training subscription agreements is recognized ratably over the subscription period.

We defer recognition of revenue from work performed on pending contract modifications until the period in which the modifications are accepted and funding is approved by the customer. Costs of work performed on pending contract modifications are expensed as incurred.

Multiple Element Arrangements

Our multiple element arrangements are from SaaS subscriptions, term license subscriptions and perpetual licenses that are generally sold in combination with maintenance and support service and frequently with professional services.

SaaS Subscriptions

For multiple element arrangements involving SaaS subscriptions that include professional services in addition to the subscription to our platform, we evaluate each element to determine whether it represents a separate unit of accounting. Because there are third-party vendors who routinely sell and provide the same professional services to our customers, our professional services are deemed to have standalone value apart from the SaaS subscription. Additionally, we offer both SaaS subscriptions and professional services on a standalone basis. Professional services revenue is therefore accounted for separately from subscription fees and recognized as the professional services are performed. We allocate revenue to the elements based on the selling price hierarchy using vendor-specific objective evidence (“VSOE”) of selling price, third-party evidence (“TPE”) of selling price, or if neither exists, best estimated selling price (“BESP”). In cases where we do not have VSOE or TPE of the elements of our arrangements, we use BESP to allocate revenue. We determine BESP for a service by considering multiple factors including, but not limited to, evaluating the weighted average of actual sales prices and other factors such as gross margin objectives, pricing practices and growth strategy. Pricing practices taken into consideration include historic contractually stated prices, volume discounts where applicable and our price lists. While we believe we can make reliable estimates regarding these matters, these estimates are inherently subjective. Once the revenue is allocated to these elements, revenue is recognized as such services are provided.

Term License Subscriptions

For multiple element arrangements involving term license subscriptions, maintenance and support and professional services, we do not have VSOE of fair value for the maintenance and support. Our term license subscriptions are generally not sold on a standalone basis, and therefore, we have not established VSOE of fair value for the subscriptions. Consequently, for our bundled arrangements that include certain professional services, there are two undelivered elements for which VSOE of fair value has not been established and, therefore, we utilize the combined services approach and defer all revenue until the software has been delivered and the provision of all services has commenced. We then recognize the entire fee from the arrangement ratably over the remaining period of the arrangement, assuming all other software revenue recognition criteria have been met.

Perpetual Licenses

For multiple element arrangements involving our perpetual software licenses, we allocate revenue to the software license arrangement by determining if VSOE of fair value exists for the undelivered elements, which are usually maintenance and support and professional services. In situations where VSOE of fair value exists for the undelivered elements, we apply the residual method whereby the fees allocated to license revenue are recognized upon delivery, the fees allocated to maintenance and support revenue are recognized over the service period and the fees allocated to professional services and training are recognized as performed. In instances where we lack VSOE of fair value for the undelivered elements, revenue is either deferred until the final element is delivered or recognized ratably over the service period when the only undelivered elements are either professional services or maintenance and support. We have VSOE for maintenance and support elements and professional services elements performed on a time and materials basis. VSOE of fair value is based upon the price charged

when the same element is sold separately. In determining VSOE of fair value, we require that a substantial majority of the selling prices fall within a reasonably narrow pricing range. We reassess VSOE annually or more frequently if required.

Deferred Revenue

Deferred revenue primarily consists of amounts billed or billable in advance of revenue recognition from our subscriptions, software, and support and professional services described above. Deferred revenue is recognized as the revenue recognition criteria are met.

Cost of Revenue

Cost of Subscriptions, Software and Support Revenue

Cost of subscriptions, software and support revenue consists primarily of fees paid to our third-party managed hosting providers and other third-party service providers, personnel costs, including payroll and benefits for our technology operations and customer support teams, and allocated facility costs and overhead.

Cost of Professional Services Revenue

Cost of professional services revenue includes all direct and indirect costs to deliver our professional services and training, including employee compensation for our global professional services and training personnel, travel costs, third-party contractor costs and allocated facility costs and overhead.

Concentration of Credit Risk

Our financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and trade accounts receivable. Deposits held with banks may exceed the amount of insurance provided on such deposits. We believe that the financial institutions that hold our cash deposits are financially sound and, accordingly, minimal credit risk exists with respect to these balances.

With regard to our customers, credit evaluation and account monitoring procedures are used to minimize the risk of loss. We believe that no additional credit risk beyond amounts provided for collection loss are inherent in accounts receivable. Revenue generated from government agencies represented 15.7%, 15.4% and 26.2% of our revenue for the years ended December 31, 2018, 2017 and 2016, respectively, of which the top three federal government agencies generated 7.8%, 8.4% and 17.7% of our revenue for the years ended December 31, 2018, 2017 and 2016, respectively. Additionally, 28.7%, 27.0% and 19.5% of our revenue during the years ended December 31, 2018, 2017 and 2016, respectively, was generated from foreign customers.

No single end-customer accounted for more than 10% of accounts receivable at December 31, 2018 or 2017.

Cash and Cash Equivalents

We consider all highly liquid investments with an original or remaining maturity of three months or less at the date of purchase, as well as overnight repurchase investments, to be cash equivalents.

Accounts Receivable and Allowance for Doubtful Accounts

Accounts receivable are stated at realizable value, net of an allowance for doubtful accounts. The allowance for doubtful accounts is based on our assessment of the collectability of accounts. We regularly review the composition of the accounts receivable aging, historical bad debts, changes in payment patterns, customer creditworthiness and current economic trends. If the financial condition of our customers were to deteriorate, resulting in their inability to make required payments, additional provisions for doubtful accounts would be required and would increase bad debt expense. To date, our allowance and related bad debt write-offs have been nominal. Activity within the allowance for doubtful accounts was as follows (in thousands):


	Year Ended December 31,
	2018		2017		2016
Balance as of January 1	$	400	$	400	$	400
Additions	211		62		7
Less write-offs, net of recoveries	(11)		(62)		(7)
Balance as of December 31	$	600	$	400	$	400

Non-trade Receivables

We record non-trade receivables to reflect amounts due for activities other than sales of subscriptions to our platform and professional services. As of December 31, 2018, our non-trade receivables related entirely to a receivable resulting from our tenant improvement allowance. The tenant improvement allowance receivable was $14.4 million as of December 31, 2018 and is classified within prepaid expenses and other current assets in the accompanying consolidated balance sheets. We recognized our initial tenant improvement allowance receivable related to our new headquarters once we took initial possession of the space in October 2018. As of December 31, 2017, we had no non-trade receivables.

Deferred Commissions

Deferred commissions are the incremental costs that are directly associated with subscription agreements with customers and consist of sales commissions paid to our direct sales force. Commissions are considered direct and incremental and as such are deferred and amortized over the terms of the related customer contracts consistent with the related revenue. Amortization of deferred commissions is included in sales and marketing expense in the accompanying consolidated statements of operations. Commission expense was $15.6 million, $11.8 million and $6.5 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Significant additions or improvements extending the useful life of an asset are capitalized, while repairs and maintenance costs which do not significantly improve the related assets or extend their useful lives are charged to expense as incurred.


Asset Category						Useful Life (in years)
Computer software						3
Computer hardware						3
Equipment						5
Office furniture and fixtures						10
Leasehold improvements						Shorter of useful life of assets or lease term

Impairment of Long-Lived Assets

Long-lived assets and certain intangible assets are reviewed for impairment whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable through undiscounted cash flows from the use of the assets. If such assets are considered to be impaired, the assets are written down to their estimated fair value. No indicators of impairment were identified for the years ended December 31, 2018, 2017 and 2016.

Fair Value of Financial Instruments

The carrying amounts of our cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate fair value as of December 31, 2018 and December 31, 2017 because of the relatively short duration of these instruments.

We use a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. The hierarchy requires us to use observable inputs when available, and to minimize the use of unobservable inputs when determining fair value. The three tiers are defined as follows:

•Level 1. Observable inputs based on unadjusted quoted prices in active markets for identical assets or liabilities;

•Level 2. Inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and

•Level 3. Unobservable inputs for which there is little or no market data, which require us to develop our own assumptions.

Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs

There were no assets or liabilities in our Level 3 instruments measured at fair value on a recurring basis during the year ended December 31, 2018.

The following table presents the changes in our Level 3 instruments measured at fair value on a recurring basis during the years ended December 31, 2017 and 2016 (in thousands):


	Year Ended December 31,
	2017		2016
Balance as of January 1,	$	850	$	650
Change in fair value of warrant liability	341		200
Reclassification of warrant liability to equity	(1,191)		—
Balance as of December 31,	$	—	$	850

Stock-Based Compensation

We account for stock-based compensation expense related to stock-based awards based on the estimated fair value of the award on the grant date. We calculate the fair value of stock options using the Black-Scholes Option Pricing Model. The fair value of RSUs is based on the closing market price of our common stock on the Nasdaq Global Market on the date of grant. For service-based awards, stock-based compensation expense is recognized on a straight-line basis over the requisite service period. For performance-based awards, stock-based compensation expense is recognized using the accelerated attribution method, based on the probability of satisfying the performance condition. For awards that contain market conditions, compensation expense is measured using a Monte Carlo simulation and recognized using the accelerated attribution method over the derived service period based on the expected market performance as of the grant date. For restricted stock units, stock-based compensation expense is recognized on a straight-line basis over the requisite service period. We account for forfeitures as they occur, rather than estimating expected forfeitures.

Basic and Diluted Loss per Common Share

We use the two-class method to compute net loss per common share because we have issued securities, other than common stock, that contractually entitle the holders to participate in dividends and earnings. These participating securities include our convertible preferred stock which have non-forfeitable rights to participate in any dividends declared on our common stock. The two-class method requires earnings for the period to be allocated between common stock and participating securities based upon their respective rights to receive distributed and undistributed earnings.

Under the two-class method, for periods with net income, basic net income per common share is computed by dividing the net income attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Net income attributable to common stockholders is computed by subtracting from net income the portion of current year earnings that the participating securities would have been entitled to receive pursuant to their dividend rights had all of the year’s earnings been distributed. No such adjustment to earnings is made during periods with a net loss, as the holders of the participating securities have no obligation to fund losses.

Diluted net income per common share is computed under the two-class method by using the weighted average number of shares of common stock outstanding, plus, for periods with net income attributable to common stockholders, the potential dilutive effects of stock options and warrants. In addition, we analyze the potential dilutive effect of the outstanding participating securities under the “if-converted” method when calculating diluted earnings per share, in which it is assumed that the outstanding participating securities convert into common stock at the beginning of the period or date of issuance, if later. We report the more dilutive of the approaches (two-class or “if-converted”) as our diluted net income per share during the period.

Due to net losses for the years ended December 31, 2018, 2017 and 2016, basic and diluted net loss per share were the same, as the effect of potentially dilutive securities would have been anti-dilutive.

Income Taxes

We use the asset and liability method of accounting for income taxes in which deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases. We measure deferred tax assets and liabilities using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be reversed. We recognize the effect on deferred tax assets and liabilities of a change in tax rates as income and expense in the period that includes the enactment date. A valuation allowance is established if it is more likely than not that all or a portion of the deferred tax asset will not be realized.

Our tax positions are subject to income tax audits by multiple tax jurisdictions throughout the world. We recognize the tax benefit of an uncertain tax position only if it is more likely than not the position is sustainable upon examination by the taxing authority. We measure the tax benefit recognized as the largest amount of benefit which is more likely than not to be realized upon settlement with the taxing authority. We recognize penalties and interest related to unrecognized tax benefits as income tax expense.

We calculate the current and deferred income tax provision based on estimates and assumptions that could differ from the actual results reflected in income tax returns filed in subsequent years and record adjustments based on filed income tax returns when identified. The amount of income taxes paid is subject to examination by U.S. federal, state and foreign tax authorities. The estimate of the potential outcome of any uncertain tax issue is subject to our assessment of relevant risks, facts and circumstances existing at that time. To the extent the assessment of such tax position changes, we record the change in estimate in the period in which we make that determination.

Segment Reporting

Operating segments are defined as components of an enterprise for which discrete financial information is available that is evaluated regularly by the chief operating decision maker (“CODM”) for purposes of allocating resources and evaluating financial performance. Our CODM is our chief executive officer, who reviews financial information presented on a companywide basis for purposes of allocating resources and evaluating financial performance. As such, our operations constitute a single operating segment and one reportable segment.

Foreign Currency

Our operations located outside of the United States where the local currency is the functional currency are translated into U.S. dollars using the current rate method. Results of operations are translated at the average rate of exchange for the period. Assets and liabilities are translated at the closing rates on the balance sheet date. Gains and losses on translation of these accounts are accumulated and reported as a separate component of stockholders’ equity (deficit) and other comprehensive loss.

Gains and losses on foreign currency transactions are recognized in the accompanying consolidated statements of operations as a component of other expense, net. Transaction gains and losses from transactions denominated in foreign currencies resulted in net transaction losses of $3.0 million for the year ended December 31, 2018, net transaction gains of $2.6 million for the year ended December 31, 2017 and net transaction losses of $1.5 million for the year ended December 31, 2016.

Research and Development

Research and development expenses include payroll, employee benefits, and other headcount-related costs associated with product development. Our product utilizes a common codebase, whether accessed by customers via the cloud or via an on-premises installation. Since our software is sold and licensed externally, we consider our software as external-use software for purposes of applying the capitalized software development guidance. Product development costs are expensed as incurred until technological feasibility has been established, which we define as the completion of all planning, designing, coding and testing activities that are necessary to establish products that meet design specifications including functions, features and technical performance requirements. We have determined that technological feasibility for our software products is reached shortly before they are released for sale. Costs incurred after technological feasibility is established are not significant, and accordingly we expense all research and development costs when incurred.

Advertising

We expense advertising costs as they are incurred. Advertising expenses were $3.9 million, $3.0 million and $1.4 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Emerging Growth Company Status

We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act (the "JOBS Act"). The JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. Thus, an emerging growth company can delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. We have elected to avail ourselves of this extended transition period and, as a result, we will not adopt new or revised accounting standards on the relevant dates on which adoption of such standards is required for other public companies.

Recent Accounting Pronouncements

Adopted

On December 22, 2017, the Tax Cuts and Jobs Act (the "TCJA") was enacted, substantially changing the U.S. Federal tax system. Notable provisions of the TCJA include the reduction of the corporate tax rate from 35% to 21% beginning in 2018, the imposition of a one-time transition tax on unremitted cumulative non-U.S. earnings of foreign subsidiaries, and the implementation of a territorial tax system. While the changes from the TCJA are generally effective beginning in 2018, U.S. GAAP accounting for income taxes requires the effect of a change in tax laws or rates to be recognized in income from continuing operations for the period that includes the enactment date. Due to the complexities involved in accounting for the enactment of the TCJA, the Securities and Exchange Commission Staff Accounting Bulletin No. 118 (“SAB 118”) allowed us to record provisional amounts in earnings for the year ended December 31, 2017. Where reasonable estimates can be made, the provisional accounting should be based on such estimates. When no reasonable estimate can be made, the provisional accounting may be based on the tax law in effect before the TCJA. We were required to complete our tax accounting for the TCJA in the period when we obtained, prepared, and analyzed the information to complete the income tax accounting. We completed our tax accounting for the TCJA in 2018.

In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting ("ASU 2017-09"), which clarifies when a change to the terms or conditions of a share-based payment award must be accounted for as a modification. ASU 2017-09 requires modification accounting if the fair value, vesting condition or the classification of the award is not the same immediately before and after a change to the terms and conditions of the award. ASU 2017-09 became effective on a prospective basis beginning on January 1, 2018. The adoption of ASU 2017-09 did not have an impact on our consolidated financial statements for the year ended December 31, 2018.

Not Yet Adopted

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which provides new guidance for revenue recognition. ASU 2014-09 provides that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 also requires improved disclosures to help users of financial statements better understand the nature, amount, timing, and uncertainty of revenue that is recognized. Entities have the option of using either a full retrospective or modified retrospective approach for the adoption of the standard. In March 2016, the FASB issued ASU No. 2016-08, Principal Versus Agent Considerations (Reporting Revenue Gross Versus Net) (“ASU 2016-08”), which clarifies implementation guidance on principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Identifying Performance Obligations and Licensing (“ASU 2016-10”), which clarifies the identification of performance obligations and the licensing implementation guidance in ASU 2014-09. In addition, in May 2016, the FASB issued ASU No. 2016-12, Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), which clarifies the guidance on assessing collectibility, presentation of sales taxes, noncash consideration and completed contracts and contract modifications at transition. For public entities, the new standard is effective for annual periods and interim periods within those annual periods, beginning after December 15, 2017. For all other entities, the new standard is effective for annual periods beginning after December 15, 2018, and interim periods within those annual periods beginning after December 15, 2019. We have elected to avail ourselves of the JOBS Act extended transition period that permits us to defer adoption until January 1, 2019. In accordance with guidance, the new standard will be adopted in our Annual Report on Form 10-K for the fiscal year ending December 31, 2019 but will not be adopted in our Quarterly Reports on Form 10-Q to be filed during 2019.

The ASU 2014-09 guidance allows two methods of adoption: retrospectively to each prior reporting period (full retrospective method) or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (modified retrospective method). We are going to adopt the new standard using the modified retrospective method.

We do not expect the new standard to have a material impact on the timing of revenue recognition related to our cloud-based subscriptions and standalone professional services. However, we expect the new standard to have a significant impact on the timing of revenue recognition related to our on-premise term license contracts. Under current industry-specific software revenue recognition guidance, we have historically concluded that we did not have VSOE of fair value of the undelivered services related to on-premise term license contracts, and accordingly, have recognized on-premise term license contracts and related services ratably over the contract term. Under this new standard, the requirement to have VSOE for undelivered services is eliminated. Therefore, we will be required to recognize a portion of revenue from the on-premise term license contracts upon delivery of the software.

In addition, we expect the new standard to impact our accounting for contract acquisition costs, both with respect to the amounts that will be capitalized as well as the period of amortization. Currently, we defer the direct and incremental commission costs to obtain a contract with a customer and amortize those costs over the term of the related customer contract consistent with the related revenue. Under the new standard, we will defer the incremental costs to obtain a contract with a customer. Therefore, the new standard will result in additional costs being capitalized, including fringe benefits. Under the new standard, initial incremental costs to obtain a contract will be amortized over the customer's estimated economic life of five years, which was calculated based on both qualitative and quantitative factors, such as product life cycles, contractual terms and customer attrition. Incremental contract costs paid relating to contract renewals will be deferred and amortized on a straight-line basis over the related renewal period. As a result, we expect the deferred commissions asset to increase and the related amortization expense in each reporting period to decrease under the new standard.

We are still in the process of quantifying the effects of the adoption of ASU 2014-09 as well as continuing to evaluate the impact of the adoption of the standard on our consolidated financial statements, including our footnotes.

In February 2016, the FASB issued ASU No. 2016-2, Leases (Topic 842) (“ASU 2016-2”), which requires that lessees recognize assets and liabilities for leases with lease terms greater than 12 months in the statement of financial position. ASU 2016-2 also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. The update is effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted. We are currently evaluating the impact the adoption of ASU 2016-2 will have on our consolidated financial statements.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326) ("ASU 2016-13"), which requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. This replaces the existing incurred loss model and is applicable to the measurement of credit losses on financial assets measured at amortized cost. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early application will be permitted for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We are currently evaluating the impact that the standard will have on our consolidated financial statements.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”), which aims to reduce the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. ASU 2016-15 will require adoption on a retrospective basis unless it is impracticable to apply, in which case we would be required to apply the amendments prospectively as of the earliest date practicable. ASU 2016-15 is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019. Early adoption is permitted. We do not expect ASU 2016-15 to have a material impact on our consolidated financial statements.

Debt	12 Months Ended
Debt	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt 2017 Financing Facility In April 2017, we entered into a financing facility consisting of a $5.0 million senior revolving credit facility, a $20.0 million senior term loan, and a $10.0 million subordinated term loan. In connection with the execution of this financing facility, our prior line of credit was terminated and we borrowed the full $20.0 million available under the senior term loan and repaid the outstanding balance under our prior term loan. Additionally, in connection with the execution of this financing facility, the lender waived the prepayment fee associated with our prior line of credit. In June 2017, we used proceeds from our IPO to pay all remaining outstanding principal and interest under the senior term loan and subsequently terminated the senior term loan and subordinated term loan. In connection with the repayment of the senior term loan, we recognized a loss on extinguishment of debt of $0.4 million related to unamortized debt issuance costs, which is included within other (income) expense, net in the accompanying consolidated statements of operations. This financing facility was terminated in November 2017 in connection with our entry into a new $20.0 million revolving line of credit. 2017 Line of Credit In November 2017, we entered into a $20.0 million revolving line of credit with a lender. The facility matures in November 2022. We may elect whether amounts drawn on the revolving line of credit bear interest at a floating rate per annum equal to either the LIBOR or the prime rate plus an additional interest rate margin that is determined by the availability of the borrowings under the revolving line of credit. The additional interest rate margin will range from 2.00% to 2.50% in the case of LIBOR advances and from 1.00% to 1.50% in the case of prime rate advances. The revolving line of credit contains an unused facility fee in an amount between 0.15% and 0.25% of the average unused portion of the revolving line of credit, which is payable quarterly. The agreement contains certain customary affirmative and negative covenants and requires us to maintain (1) an adjusted quick ratio of at least 1.35 to 1.0 and (ii) minimum adjusted EBITDA in the amounts and for the periods set forth in the agreement. Any amounts borrowed under the credit facility are collateralized by substantially all of our assets. We were in compliance with all covenants as of December 31, 2018. As of December 31, 2018, we had no outstanding borrowings under the revolving line of credit.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

For the years ended December 31, 2018, 2017 and 2016, our loss before income taxes was comprised of the following (in thousands):


	2018		2017		2016
Domestic	$	(30,663)	$	(23,093)	$	(4,524)
Foreign	(18,549)		(7,153)		(9,620)
Total	$	(49,212)	$	(30,246)	$	(14,144)

For the years ended December 31, 2018, 2017 and 2016, our income tax expense (benefit) was comprised of the following (in thousands):


	2018		2017		2016
Current:
Federal	$	—	$	(65)	$	(627)
State	25		68		(200)
Foreign	432		1,009		266
Total current expense (benefit)	457		1,012		(561)
Deferred:
Federal	—		(42)		(922)
State	—		—		(230)
Foreign	(218)		(209)		30
Total deferred expense (benefit)	(218)		(251)		(1,122)
Total income tax expense (benefit)	$	239	$	761	$	(1,683)

On December 22, 2017, U.S. federal tax reform was enacted with the signing of the TCJA. Notable provisions of the TCJA include the following:

•Establishment of a flat corporate income tax rate of 21% on U.S. earnings;

•Imposition of a one-time tax on unremitted cumulative non-U.S. earnings of foreign subsidiaries, or the Transition Tax;

•The imposition of a new minimum tax on certain non-U.S. earnings, irrespective of the territorial system of taxation, and generally allows for the repatriation of future earnings of foreign subsidiaries without incurring additional U.S. taxes by transitioning to a territorial system of taxation;

•Imposition of minimum taxes on certain payments made by a U.S. company to a related foreign company, or the Base Erosion Anti-Abuse Tax;

•Elimination of the alternative minimum tax and allowance of a refund for previous alternative minimum tax credits;

•Allowance for immediate expensing of the cost of investments in certain depreciable assets acquired and placed in service after September 27, 2017; and

•Reduction in tax deductions with respect to certain compensation paid to certain executive officers.

While the changes from the TCJA are generally effective beginning in 2018, U.S. GAAP accounting for income taxes requires the effect of a change in tax laws or rates to be recognized in income from continuing operations for the period that includes the enactment date. Due to the complexities involved in accounting for the enactment of the TCJA, SAB 118 allowed us to record provisional amounts in earnings for the year ended December 31, 2017.

During 2018, we recorded tax charges for the impact of the TCJA effects using the current available information and technical guidance on the interpretations of the TCJA. As permitted by SAB 118, we recorded provisional estimates and have subsequently finalized our accounting analysis based on the guidance, interpretations, and data available. Adjustments made in the fourth quarter of the year ended December 31, 2018, upon finalization of our accounting analysis, were not material to our consolidated financial statements.

For the years ended December 31, 2018, 2017 and 2016, the provision for income taxes differs from the amount computed by applying the federal statutory income tax rates to our loss before the provision (benefit) for income taxes, as follows:


	2018		2017		2016
U.S. federal statutory tax rate	21.0	%	34.0	%	34.0	%
State tax expense	7.2		4.9		1.4
Foreign rate differential	(5.1)		(6.7)		(17.8)
Nondeductible expenses	(0.7)		(0.9)		(2.3)
Equity compensation	9.5		—		—
Tax credits	3.9		5.8		6.5
Unrecognized tax benefits	(0.8)		(0.7)		(0.2)
Other	0.6		(0.3)		(0.2)
Remeasurement of deferred taxes	—		(7.0)		—
Change in valuation allowance	(36.0)		(31.6)		(9.6)
Total	(0.4)	%	(2.5)	%	11.8	%

Deferred tax assets and liabilities reflect the net tax effects of temporary differences between the carrying amount of the assets and liabilities for financial reporting purposes and the amounts used for income tax purposes.

As of December 31, 2018 and 2017, significant components of our deferred tax assets and liabilities were as follows (in thousands):


	2018		2017
Deferred tax assets:
Net operating losses	$	21,059	$	10,413
Tax credits	5,945		4,169
Deferred revenue	4,179		1,248
Equity compensation	3,923		1,207
Accrued vacation	1,170		967
Deferred rent	373		473
Bad debt	164		109
Depreciation	151		—
Other	548		287
Gross deferred tax assets	37,512		18,873
Less: Valuation allowance	(30,039)		(12,328)
Total deferred tax assets	7,473		6,545
Deferred tax liabilities:
Prepaid expenses	(6,640)		(5,614)
Unbilled receivables	(419)		(555)
Depreciation	—		(174)
Other	(130)		(8)
Total deferred tax liabilities	(7,189)		(6,351)
Net deferred tax asset	$	284	$	194

As of December 31, 2018 and 2017, we had $56.9 million and $25.3 million of gross net operating loss (“NOL”) carryforwards for U.S. federal tax purposes, respectively. Federal NOL carryforwards generated prior to 2018 will expire, if unused, in 2037. As of December 31, 2018 and 2017, we had U.S. gross state NOL carryforwards of $57.2 million and $25.3 million, respectively. We had tax effected state NOL carryforwards of $3.7 million and $1.6 million as of December 31, 2018

and 2017, respectively. U.S. state NOL carryforwards will substantially expire, if unused, in 2038. As of December 31, 2018 and 2017, we had foreign NOL carryforwards of $56.3 million and $35.7 million, respectively, primarily attributable to our subsidiary in Switzerland. Those NOL carryforwards will substantially expire, if unused, in 2025.

Section 382 of the Internal Revenue Code limits the utilization of the NOLs when ownership changes occur, as defined by that section. A number of states have similar state laws that limit utilization of the state NOLs when ownership changes occur. We have performed an analysis of our Section 382 ownership changes and have determined that all federal and U.S state NOLs are available for use as of December 31, 2018.

As of December 31, 2018 and 2017, we had $6.4 million and $4.5 million, respectively, of federal tax credit carryforwards which will expire, if unused, in 2038.

The net change during the year in the total valuation allowance was $17.7 million, primarily driven by the valuation allowance recorded against the U.S. deferred tax assets and the change in the Switzerland deferred tax assets.

We continue to maintain a full valuation allowance against U.S. deferred tax assets based on our cumulative operating results as of December 31, 2018, three-year cumulative loss, and assessment of our expected future results of operations. We have evaluated all evidence, both positive and negative, in assessing the likelihood of realizability and the negative evidence outweighed the positive evidence.

As of December 31, 2018, we have a valuation allowance of $5.3 million against foreign deferred tax assets, primarily for deferred tax assets at our subsidiary in Switzerland. We continue to maintain a full valuation allowance on the deferred tax assets of our subsidiary in Switzerland as we determined that it was not more likely than not that we would be able to realize a benefit from the NOL at that subsidiary. Based on our cumulative operating results as of December 31, 2018, and assessment of our expected future results of operations, we determined that it was not more likely than not that we would be able to realize the deferred tax assets prior to expiration.

We are subject to income taxes in the United States, Australia, Canada, France, Germany, Italy, Netherlands, Switzerland, Singapore, Sweden and the United Kingdom.

We plan to distribute previously undistributed earnings of our foreign subsidiaries back to the United States in future years. Upon repatriation of those earnings, if any, we may be subject to taxes, including withholding taxes, net of any applicable foreign tax credits. Determination of the amount of unrecognized deferred U.S. income tax liability is not practicable.

As of December 31, 2018 and 2017, we had unrecognized tax benefits of $1.0 million and $0.7 million, respectively, of which the entire portion would affect our effective tax rate if recognized. The following table summarizes the activity related to our unrecognized tax benefit from January 1, 2016 to December 31, 2018 (in thousands):


Balance as of January 1, 2016	$	384
Additions for tax positions in current years	171
Additions for tax positions in prior years	—
Reductions due to lapse in statutes of limitations	(136)
Settlements	—
Balance as of December 31, 2016	419
Additions for tax positions in current years	232
Additions for tax positions in prior years	—
Reductions due to lapse in statutes of limitations	—
Settlements	—
Balance as of December 31, 2017	651
Additions for tax positions in current years	388
Additions for tax positions in prior years	—
Reductions due to lapse in statutes of limitations	—
Settlements	—
Balance as of December 31, 2018	$	1,039

We recognize interest and penalties related to uncertain tax positions in income tax expense. During the year ended December 31, 2018, we did not accrue additional interest. During the year ended December 31, 2017, we reduced our liability for potential interest and penalties by $2,000. During the year ended December 31, 2016, we recognized potential interest and penalties of $2,000. The cumulative balance of interest and penalties as of each of December 31, 2018 and 2017 was $33,000. If recognized, approximately $1.0 million of unrecognized tax benefits would impact the effective tax rate.

We anticipate that total unrecognized tax benefits will not decrease over the next year.

We file income tax returns in the United States federal jurisdiction and in many state and foreign jurisdictions. The tax years 2014 through 2018 remain open to examination by the major taxing jurisdictions to which we are subject. No material examinations are currently open.

On June 21, 2018, the U. S. Supreme Court issued its decision in South Dakota v. Wayfair, Inc., which overturned prior case law that held that out-of-state merchants were not required to collect sales taxes unless they had a physical presence in the buyer’s state. We have analyzed the impact of this decision and do not anticipate it to have a significant impact on our operations.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

In May 2017, our board of directors adopted, and our stockholders approved, the 2017 Equity Incentive Plan (the “2017 Plan”). The 2017 Plan provides for the grant of incentive stock options to employees, and for the grant of nonstatutory stock options, restricted stock awards, restricted stock unit awards, stock appreciation rights, performance-based stock awards and other forms of equity compensation to employees, including officers, and to non-employee directors and consultants. We initially reserved 6,421,442 shares of Class A common stock for issuance under the 2017 Plan, which included 421,442 shares that remained available for issuance under our 2007 Stock Option Plan (the “2007 Plan”) at the time that the 2017 Plan became effective. The number of shares reserved under the 2017 Plan increases for any shares subject to outstanding awards originally granted under the 2007 Plan that expire or are forfeited prior to exercise. As a result of the adoption of the 2017 Plan, no further grants may be made under the 2007 Plan. As of December 31, 2018, there were 7,040,863 shares of Class A common stock reserved for issuance under the 2017 Plan, of which 5,680,655 were available to be issued.

The 2007 Plan provided for the grant of stock options to employees, directors, and officers. Stock options under the 2007 Plan are exercisable into shares of Class B common stock and generally expire ten years from the date of grant. Under the 2007 Plan, the exercise price of each award was established by the board of directors but could not be less than the fair market value of a share of our common stock on the grant date. Stock options generally vest upon the satisfaction of both a service condition and a performance condition. The service condition is satisfied at various rates as determined by us, typically on an

annual basis over five years. The performance condition required the occurrence of a qualifying event, defined as a change of control transaction or upon the completion of an IPO. The performance condition was satisfied upon the completion of our IPO in May 2017, on which date we recognized $6.2 million of cumulative stock-based compensation expense using the accelerated attribution method from the service start date.

We estimate the fair value of stock options using the Black-Scholes Option Pricing Model, which requires the use of subjective assumptions, including the expected term of the option, the current price of the underlying stock, the expected stock price volatility, expected dividend yield and the risk-free interest rate for the expected term of the option. The expected term represents the period of time the stock options are expected to be outstanding. Due to the lack of sufficient historical exercise data to provide a reasonable basis upon which to otherwise estimate the expected term of the stock options, we use the simplified method to estimate the expected term for our stock options. Under the simplified method, the expected term of an option is presumed to be the mid-point between the vesting date and the end of the contractual term. Expected volatility is based on historical volatilities for publicly traded stock of comparable companies over the estimated expected term of the stock options. We assume no dividend yield because dividends are not expected to be paid in the near future, which is consistent with our history of not paying dividends.

The following table summarizes the assumptions used to estimate the fair value of stock options granted during the years ended December 31:


	2018	2017	2016
Risk-free interest rate	*	1.9% - 2.2%	1.3% - 1.5%
Expected term (in years)	*	6.5	6.5
Expected volatility	*	38.1% - 40.6%	40.9% - 42.0%
Expected dividend yield	*	—%	—%

* Not applicable because no stock options were granted during the period.

Stock Options

The following table summarizes the stock option activity for the years ended December 31, 2018 and 2017:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2017	6,784,448	$	4.65	6.5	$	44,259
Granted	1,256,200	11.92
Exercised	(876,121)	1.27			14,807
Canceled	(153,640)	7.29
Outstanding at December 31, 2017	7,010,887	6.36		6.6	176,122
Granted	—	—
Exercised	(1,486,218)	2.10			41,606
Canceled	(503,601)	9.51
Outstanding at December 31, 2018	5,021,068	7.30		6.4	97,440
Exercisable at December 31, 2018	3,448,348	6.21		5.9	70,682

The weighted average grant-date fair value of options granted during the years ended December 31, 2017 and 2016 was $5.05 and $4.35 per option, respectively. No stock options were granted during the year ended December 31, 2018. The total fair value of stock options that vested during the years ended December 31, 2018 and 2017 was $10.5 million and $5.6 million, respectively. No stock options vested during the year ended December 31, 2016 because a qualifying event had not yet occurred. As of December 31, 2018, the total compensation cost related to unvested stock options not yet recognized was $2.6 million, which will be recognized over a weighted average period of 2.1 years.

On April 25, 2017, our board of directors modified certain outstanding stock options nearing their expiration date to remove the performance condition. Stock options to purchase an aggregate of 216,160 shares of common stock were modified, and we recognized stock-based compensation expense of $2.4 million related to this modification.

In July 2016, our board of directors granted a stock option to purchase 1,828,080 shares of our Class A common stock to our Chief Executive Officer (the "2016 CEO Grant") under the 2007 Plan with an exercise price of $9.46 per share. The 2016 CEO Grant was eligible to vest based on the achievement of a stock price appreciation target of our Class A common stock. The fair value of the 2016 CEO Grant was determined using a Monte Carlo simulation. During the year ended December 31, 2018, the market-based milestone of the 2016 CEO Grant was achieved, resulting in 1,828,080 shares vesting and becoming exercisable. Stock-based compensation expense recognized for the 2016 CEO Grant was $5.6 million and $2.7 million for the years ended December 31, 2018 and 2017, respectively.

In December 2018, we entered into a stock option cancellation agreement with our Chief Executive Officer, pursuant to which vested options to purchase 383,897 shares of Class A common stock were canceled. The remaining options granted under the 2016 CEO Grant were unaffected. No compensation expense was recorded as the canceled stock options were fully vested at the time.

Restricted Stock Units

The following table summarizes the restricted stock unit activity for the years ended December 31, 2018 and 2017:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2017	—	$	—
Granted	738,055	22.15
Vested	(4,930)	20.24
Canceled	(1,150)	21.40
Non-vested outstanding at December 31, 2017	731,975	22.16
Granted	622,166	29.60
Vested	(143,390)	22.19
Canceled	(35,702)	23.97
Non-vested outstanding at December 31, 2018	1,175,049	26.04

As of December 31, 2018, total unrecognized compensation cost related to unvested restricted stock units was approximately $25.4 million and the weighted average remaining vesting period was 2.0 years.

In November 2018, our board of directors approved the grant of 255,930 restricted stock units under the 2017 Plan at a fair value of $30.06 per share to our three co-founders. The value of these awards at the grant date was $7.7 million and will be amortized over the vesting periods. The restricted stock units will vest during the three months ended March 31, 2019.

The following table summarizes the components of our stock-based compensation expense for the years ended December 31, 2018 and 2017 (in thousands):


	2018		2017
Stock-based compensation expense related to stock options	$	7,947	$	9,607
Stock-based compensation expense related to restricted stock units	7,714		753
Stock-based compensation expense related to the issuance of common stock to directors	393		222
Stock-based compensation expense related to stock option modifications	—		2,394
Total stock-based compensation expense	$	16,054	$	12,976

Stock-based compensation expense for restricted stock units, stock options and issuances of common stock is included in the following line items in the accompanying consolidated statements of operations for the years ended December 31, 2018 and 2017 (in thousands):


	2018		2017
Cost of revenue
Subscriptions, software and support	$	514	$	575
Professional services	1,717		1,295
Operating expenses
Sales and marketing	3,473		3,233
Research and development	2,416		2,822
General and administrative	7,934		5,051
Total stock-based compensation expense	$	16,054	$	12,976

For the year ended December 31, 2016, no stock-based compensation expense was recognized for our stock option awards because a qualifying event had not yet occurred.

Stockholders’ Equity	12 Months Ended
Stockholders’ Equity	Dec. 31, 2018
Equity [Abstract]
Stockholders’ Equity	Stockholders’ Equity Convertible Preferred Stock Immediately prior to the completion of the IPO, all shares of convertible preferred stock then outstanding were automatically converted into 18,163,158 shares of common stock on a one-for-one basis, and then reclassified as shares of Class B common stock. No convertible preferred stock was outstanding as of December 31, 2018 or 2017. Common Stock As of December 31, 2018, we had authorized 500,000,000 shares of Class A common stock and 100,000,000 shares of Class B common stock, each with a par value of $0.0001 per share, of which 29,626,054 shares of Class A common stock and 34,290,383 shares of Class B common stock were issued and outstanding. The rights of the holders of Class A common stock and Class B common stock are identical, except with respect to voting and conversion rights. The holders of Class A common stock are entitled to one vote per share, and the holders of Class B common stock are entitled to ten votes per share, on all matters that are subject to stockholder vote. The holders of Class B common stock also have approval rights for certain corporate actions. Each share of Class B common stock may be converted into one share of Class A common stock at the option of its holder and will be automatically converted into one share of Class A common stock upon transfer thereof, subject to certain exceptions. In addition, upon the date on which the outstanding shares of Class B common stock represent less than 10% of the aggregate voting power of our capital stock, all outstanding shares of Class B common stock shall convert automatically into Class A common stock. Warrants We previously issued a warrant to purchase 84,360 shares of Series A convertible preferred stock in conjunction with a credit facility with a lender at an exercise price of $0.88905 per share. Immediately prior to the completion of the IPO, this warrant was converted into a warrant to purchase 84,360 shares of Class B common stock. The fair value at the time of the conversion was $1.2 million and was recorded as additional paid-in capital and a reduction of the preferred stock warrant liability. In May 2017, the warrant holder exercised the warrant and we issued 79,363 shares of Class B common stock through a cashless exercise of the warrant, in accordance with its terms. No warrants were outstanding as of December 31, 2018 or 2017.

Basic and Diluted Loss per Common Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Basic and Diluted Loss per Common Share

The following table sets forth the computation of basic and diluted net loss per share for the years ended December 31 (in thousands, except per share data):


	Year Ended December 31,
	2018		2017		2016
Numerator:
Net loss	$	(49,451)	$	(31,007)	$	(12,461)
Accretion of dividends on convertible preferred stock	—		357		857
Net loss attributable to common stockholders	$	(49,451)	$	(31,364)	$	(13,318)
Denominator
Weighted average common shares outstanding, basic and diluted	62,140,684		49,529,833		34,274,718
Net loss per share attributable to common stockholders, basic and diluted	$	(0.80)	$	(0.63)	$	(0.39)

The following securities have been excluded from the calculation of weighted average common shares outstanding because the effect is anti-dilutive or performance or market conditions had not been met at the end of the period:


	Year Ended December 31,
	2018	2017	2016
Convertible preferred stock:
Series A convertible preferred stock	—	—	12,043,108
Series B convertible preferred stock	—	—	6,120,050
Warrant to purchase Series A convertible preferred stock	—	—	84,360
Stock options	5,021,068	7,010,887	6,784,448
Restricted stock units	1,175,049	731,975	—

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

We lease office space and equipment in our headquarters location in Reston, Virginia, as well as in the United Kingdom, France, Germany, Canada, Italy, Australia, the Netherlands and Singapore, under non-cancellable operating lease agreements which have various expiration dates through 2031 for our office space and various expiration dates through 2020 for our equipment.

In April 2018, we entered into a new lease agreement for a new headquarters in Tysons, Virginia. We took initial possession of the first phase of the new headquarters in October 2018 and began to recognize rent expense. We expect to start making recurring rental payments under the lease in the third quarter of 2020. Total payments committed under the lease amount to $87.2 million. In connection with the lease agreement, we also entered into a letter of credit of $9.4 million to fund the security deposit required by the lease.

The lease for the new headquarters contains a tenant improvement allowance of up to $18.4 million from the landlord. The tenant improvement allowance is accounted for as a lease incentive obligation and is amortized as a reduction to rent expense over the lease term. We recorded a lease incentive obligation when we took initial possession of the first phase of the new headquarters. As of December 31, 2018, $1.2 million was included in other current liabilities and $14.4 million was included in deferred rent, net of current portion on the accompanying consolidated balance sheets.

Lease Related Commitments

Lease related commitments include payments to third-party vendors for services related to our new headquarters.

A summary of our future minimum lease commitments and other commitments by year as of December 31, 2018 is as follows (in thousands):


	Office Leases		Equipment Leases		Lease Related Commitments
2019	$	6,985	$	216	$	29,587
2020	6,371		22		—
2021	8,331		—		—
2022	6,939		—		—
2023	6,987		—		—
Thereafter	65,151		—		—
	100,764		238		29,587
Less: tenant improvement allowance	—		—		(14,441)
Total	$	100,764	$	238	$	15,146

We record rent expense using the total minimum rent commitment, amortized using the straight-line method over the term of the lease. The difference between monthly rental payments and recorded rent expense is charged to deferred rent. As of December 31, 2018 and 2017, deferred rent totaled $17.4 million and $2.0 million, respectively, and is included within other current liabilities and deferred rent, net of current portion on the accompanying consolidated balance sheets. In addition to rental payments, certain leases require additional payments for real estate taxes, common area maintenance and insurance, which are expensed when incurred and not included in the future minimum payments.

Total rent and lease expense was $8.8 million, $7.0 million and $6.6 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Other Commitments

We also have entered into a non-cancellable agreement for the use of technology that is integral in the development of our software and pay annual royalty fees of $0.3 million.

Letters of Credit

As of December 31, 2018 and 2017, we had outstanding letters of credit totaling $10.5 million and $1.1 million, respectively, in connection with securing our leased office space. All letters of credit are secured by our borrowing arrangement as described in Note 5.

Legal

From time to time, we are subject to legal, regulatory and other proceedings and claims that arise in the ordinary course of business. There are no issues or resolution of any matters that are expected to have a material adverse impact on our consolidated financial statements.

Segment and Geographic Information

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Segment and Geographic Information

The following table summarizes revenue by geography for the years ended December 31 (in thousands):


	2018		2017		2016
Domestic	$	161,716	$	128,997	$	107,069
International	65,027		47,740		25,854
Total	$	226,743	$	176,737	$	132,923

With respect to geographic information, revenue is attributed to respective geographies based on the contracting address of the customer. There were no individual foreign countries from which more than 10% of our total revenue was attributable for the years ended December 31, 2018, 2017 and 2016. Substantially all of our long-lived assets were held in the United States as of December 31, 2018 and December 31, 2017.

Retirement Plans	12 Months Ended
Retirement Plans	Dec. 31, 2018
Retirement Benefits [Abstract]
Retirement Plans	Retirement PlansWe have a defined contribution 401(k) retirement and savings plan (the “401(k) Plan”) to provide retirement benefits for all eligible employees. All employees who have completed forty-five days of service and are at least twenty-one years of age are eligible to participate in the 401(k) Plan. The 401(k) Plan allows eligible employees to make salary-deferred contributions up to 75% of their annual compensation, as defined, and subject to certain Internal Revenue Service limitations. Employer contributions vest at 25% per year, over four years. For the years ending December 31, 2018, 2017 and 2016, we incurred $4.7 million, $3.3 million and $2.6 million, respectively, in contribution expense related to the employer matching contributions. We are obligated to make plan contributions for the employees of certain of our wholly-owned foreign subsidiaries. For the years ending December 31, 2018, 2017 and 2016, we incurred $1.3 million, $0.9 million and $0.7 million, respectively, in contribution expense related to our foreign subsidiaries.

Selected Quarterly Information (Unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Information (Unaudited)

The following table sets forth unaudited quarterly consolidated statement of operations data for each of the eight quarters in 2018 and 2017. The information for each of these quarters has been prepared on the same basis as the audited annual consolidated financial statements included in this Annual Report on Form 10-K. In our opinion, the quarterly financial data reflects all adjustments, which consist only of normal recurring adjustments that we consider necessary for a fair presentation of this data. The quarterly financial data should be read in conjunction with our consolidated financial statements and related notes included elsewhere in this Annual Report on Form 10-K. These quarterly results are not necessarily indicative of our operating results to be expected in the future.


	Three Months Ended
	Dec 31, 2018		Sep 30, 2018		Jun 30, 2018		Mar 31, 2018		Dec 31, 2017		Sep 30, 2017		Jun 30, 2017		Mar 31, 2017
	(in thousands)
	(unaudited)
Consolidated Statements of
Operations Data:
Revenue:
Subscriptions, software and support	$	35,108	$	30,905	$	33,047	$	26,952	$	25,398	$	22,660	$	22,012	$	21,444
Professional services	25,108		24,043		26,836		24,744		25,164		21,988		21,186		16,885
Total revenue	60,216		54,948		59,883		51,696		50,562		44,648		43,198		38,329
Cost of revenue:
Subscriptions, software and support	3,284		3,261		2,824		2,628		2,488		2,341		2,488		2,062
Professional services	18,926		16,831		18,750		18,421		16,169		14,272		14,149		10,628
Total cost of revenue	22,210		20,092		21,574		21,049		18,657		16,613		16,637		12,690
Gross profit	38,006		34,856		38,309		30,647		31,905		28,035		26,561		25,639
Operating expenses:
Sales and marketing	30,177		25,467		27,384		22,964		22,463		19,725		22,775		17,003
Research and development	12,332		11,737		10,785		9,870		8,968		8,596		9,971		7,300
General and administrative	8,799		12,537		8,425		8,060		7,429		6,237		8,635		4,849
Total operating expenses	51,308		49,741		46,594		40,894		38,860		34,558		41,381		29,152
Operating loss	(13,302)		(14,885)		(8,285)		(10,247)		(6,955)		(6,523)		(14,820)		(3,513)
Other expense (income):
Other expense (income), net	510		110		2,593		(918)		(380)		(425)		(734)		(499)
Interest expense (income)	64		67		54		13		22		(2)		197		256
Total other expense (income)	574		177		2,647		(905)		(358)		(427)		(537)		(243)
Loss before income taxes	(13,876)		(15,062)		(10,932)		(9,342)		(6,597)		(6,096)		(14,283)		(3,270)
Income tax expense (benefit)	27		(34)		35		211		272		188		176		125
Net loss ⁽¹⁾⁽²⁾	$	(13,903)	$	(15,028)	$	(10,967)	$	(9,553)	$	(6,869)	$	(6,284)	$	(14,459)	$	(3,395)

(1) In the second quarter of 2017, we recorded $6.2 million of cumulative stock-based compensation expense upon the

effectiveness of our IPO and $2.4 million of stock-based compensation expense related to the stock option modifications.

See Note 7 for further discussion of stock-based compensation expense.

Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying consolidated financial statements and footnotes have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) as contained in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (the “Codification” or “ASC”)
Use of Estimates	Use of Estimates The preparation of our consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and judgments that affect the amounts reported in these consolidated financial statements and accompanying notes. Although we believe that the estimates we use are reasonable, due to the inherent uncertainty involved in making these estimates, actual results reported in future periods could differ from those estimates. Significant estimates embedded in the consolidated financial statements include revenue recognition, income taxes and the related valuation allowance, stock-based compensation and fair value measurements for our common stock and preferred stock warrant.
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Appian and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Initial Public Offering	Public Offering In August 2018, we completed an underwritten public offering of 2,000,000 shares of our Class A common stock, of which 1,675,000 shares of Class A common stock were sold by us and 325,000 shares of Class A common stock were sold by existing stockholders, at on offering price to the public of $35.15 per share. Our net proceeds from the offering were $57.8 million, after deducting underwriting discounts and commissions and offering expenses. We did not receive any of the proceeds from the sale of shares by the selling stockholders.
Revenue Recognition	Revenue Recognition We generate revenue primarily through sales of subscriptions to our platform, as well as professional services. To a lesser extent, we also generate revenue from the sale of perpetual software license agreements and associated maintenance and support. We recognize revenue when all of the following conditions are met: (1) there is persuasive evidence of an arrangement; (2) the service or product has been provided to the customer; (3) the amount of fees to be paid by the customer is fixed or determinable; and (4) the collection of related fees is reasonably assured. If collection is not reasonably assured, we defer revenue recognition until collectability becomes reasonably assured. Our arrangements do not contain rights of return. Revenue is recognized net of any taxes collected from customers and subsequently remitted to governmental authorities. Subscriptions, Software and Support Revenue Subscriptions, software and support revenue is primarily related to (1) software as a service (“SaaS”) subscriptions bundled with maintenance and support and hosting services and (2) term license subscriptions bundled with maintenance and support. To a lesser extent, we also generate revenue from the sale of perpetual software licenses and associated maintenance and support. Historically, we licensed our software primarily under perpetual licenses, but over time we transitioned from perpetual licenses to subscriptions. Revenue from our perpetual software licenses was 2.0% of our total revenue for 2018. Revenue from our perpetual software licenses was less than 1.0% of our total revenue for each of 2017 and 2016. We generally charge subscription fees on a per-user basis and, to a lesser degree, non-user based single application licenses. We bill customers and collect payment for subscriptions to our platform in advance on a monthly, quarterly or annual basis. In certain instances, we have had customers pay their entire contract up front. SaaS Subscriptions Our SaaS subscription revenue is derived from customers accessing our cloud offering pursuant to contracts that are generally one to five years in length. We perform all required maintenance and support for our cloud offering and we do not separately charge customers for hosting costs. In these arrangements, our customers do not have the right to take the software on-premises and, as a result, such arrangements are not accounted for within the scope of the software revenue guidance. Revenue from SaaS subscriptions is recognized ratably over the term of the subscription, beginning with the date our service is made available to our customer. Term License Subscriptions Our term license subscription revenue is derived from customers with on-premises installations of our platform pursuant to contracts that are generally one to five years in length. Customers with term license subscriptions have the right to use our software and receive maintenance and support. Since we do not sell maintenance and support separately from the subscription, revenue for the term license subscription and maintenance and support is recognized ratably over the term of the subscription, upon delivery of the platform to the customer when sold on a standalone basis. Perpetual Licenses Our perpetual license revenue is derived from customers with perpetual licenses to our platform and associated maintenance and support contracts. We recognize revenue from perpetual licenses on the date of delivery to our customer. We sell maintenance and support to perpetual license customers separately from the perpetual licenses pursuant to agreements that generally renew annually. Maintenance and support revenue is deferred and recognized ratably over the term of the support period. Professional Services Our professional services revenue is comprised of fees for consulting services, including application development and deployment assistance and training related to our platform. Our professional services are not essential to the functionality of our platform because the platform is ready for the customer’s use immediately upon delivery and is not modified or customized in any manner. Consulting services are billed under both time-and-material and fixed-fee arrangements. For standalone time-and-material contracts, we recognize revenue at contractually agreed upon billing rates applied to hours performed. For standalone fixed-fee contracts, we also recognize revenue as the work is performed using the proportional performance method of accounting. Training revenue is recognized when the associated training services are delivered. Training is also sold in the form of a subscription arrangement where a customer agrees to pay an annual fixed fee for a fixed number of users to have access to all of our training offerings during the year. Revenue from training subscription agreements is recognized ratably over the subscription period. We defer recognition of revenue from work performed on pending contract modifications until the period in which the modifications are accepted and funding is approved by the customer. Costs of work performed on pending contract modifications are expensed as incurred. Multiple Element Arrangements Our multiple element arrangements are from SaaS subscriptions, term license subscriptions and perpetual licenses that are generally sold in combination with maintenance and support service and frequently with professional services. SaaS Subscriptions For multiple element arrangements involving SaaS subscriptions that include professional services in addition to the subscription to our platform, we evaluate each element to determine whether it represents a separate unit of accounting. Because there are third-party vendors who routinely sell and provide the same professional services to our customers, our professional services are deemed to have standalone value apart from the SaaS subscription. Additionally, we offer both SaaS subscriptions and professional services on a standalone basis. Professional services revenue is therefore accounted for separately from subscription fees and recognized as the professional services are performed. We allocate revenue to the elements based on the selling price hierarchy using vendor-specific objective evidence (“VSOE”) of selling price, third-party evidence (“TPE”) of selling price, or if neither exists, best estimated selling price (“BESP”). In cases where we do not have VSOE or TPE of the elements of our arrangements, we use BESP to allocate revenue. We determine BESP for a service by considering multiple factors including, but not limited to, evaluating the weighted average of actual sales prices and other factors such as gross margin objectives, pricing practices and growth strategy. Pricing practices taken into consideration include historic contractually stated prices, volume discounts where applicable and our price lists. While we believe we can make reliable estimates regarding these matters, these estimates are inherently subjective. Once the revenue is allocated to these elements, revenue is recognized as such services are provided. Term License Subscriptions For multiple element arrangements involving term license subscriptions, maintenance and support and professional services, we do not have VSOE of fair value for the maintenance and support. Our term license subscriptions are generally not sold on a standalone basis, and therefore, we have not established VSOE of fair value for the subscriptions. Consequently, for our bundled arrangements that include certain professional services, there are two undelivered elements for which VSOE of fair value has not been established and, therefore, we utilize the combined services approach and defer all revenue until the software has been delivered and the provision of all services has commenced. We then recognize the entire fee from the arrangement ratably over the remaining period of the arrangement, assuming all other software revenue recognition criteria have been met. Perpetual Licenses For multiple element arrangements involving our perpetual software licenses, we allocate revenue to the software license arrangement by determining if VSOE of fair value exists for the undelivered elements, which are usually maintenance and support and professional services. In situations where VSOE of fair value exists for the undelivered elements, we apply the residual method whereby the fees allocated to license revenue are recognized upon delivery, the fees allocated to maintenance and support revenue are recognized over the service period and the fees allocated to professional services and training are recognized as performed. In instances where we lack VSOE of fair value for the undelivered elements, revenue is either deferred until the final element is delivered or recognized ratably over the service period when the only undelivered elements are either professional services or maintenance and support. We have VSOE for maintenance and support elements and professional services elements performed on a time and materials basis. VSOE of fair value is based upon the price charged when the same element is sold separately. In determining VSOE of fair value, we require that a substantial majority of the selling prices fall within a reasonably narrow pricing range. We reassess VSOE annually or more frequently if required.
Deferred Revenue	Deferred Revenue Deferred revenue primarily consists of amounts billed or billable in advance of revenue recognition from our subscriptions, software, and support and professional services described above. Deferred revenue is recognized as the revenue recognition criteria are met.
Cost of Revenue	Cost of Revenue Cost of Subscriptions, Software and Support Revenue Cost of subscriptions, software and support revenue consists primarily of fees paid to our third-party managed hosting providers and other third-party service providers, personnel costs, including payroll and benefits for our technology operations and customer support teams, and allocated facility costs and overhead. Cost of Professional Services Revenue Cost of professional services revenue includes all direct and indirect costs to deliver our professional services and training, including employee compensation for our global professional services and training personnel, travel costs, third-party contractor costs and allocated facility costs and overhead.
Concentration of Credit Risk	Concentration of Credit Risk Our financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and trade accounts receivable. Deposits held with banks may exceed the amount of insurance provided on such deposits. We believe that the financial institutions that hold our cash deposits are financially sound and, accordingly, minimal credit risk exists with respect to these balances.
Cash and Cash Equivalents	Cash and Cash EquivalentsWe consider all highly liquid investments with an original or remaining maturity of three months or less at the date of purchase, as well as overnight repurchase investments, to be cash equivalents.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful AccountsAccounts receivable are stated at realizable value, net of an allowance for doubtful accounts. The allowance for doubtful accounts is based on our assessment of the collectability of accounts. We regularly review the composition of the accounts receivable aging, historical bad debts, changes in payment patterns, customer creditworthiness and current economic trends. If the financial condition of our customers were to deteriorate, resulting in their inability to make required payments, additional provisions for doubtful accounts would be required and would increase bad debt expense. To date, our allowance and related bad debt write-offs have been nominal.
Deferred Commissions	Deferred CommissionsDeferred commissions are the incremental costs that are directly associated with subscription agreements with customers and consist of sales commissions paid to our direct sales force. Commissions are considered direct and incremental and as such are deferred and amortized over the terms of the related customer contracts consistent with the related revenue. Amortization of deferred commissions is included in sales and marketing expense in the accompanying consolidated statements of operations.
Property, Plant and Equipment	Property and EquipmentProperty and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Significant additions or improvements extending the useful life of an asset are capitalized, while repairs and maintenance costs which do not significantly improve the related assets or extend their useful lives are charged to expense as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived AssetsLong-lived assets and certain intangible assets are reviewed for impairment whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable through undiscounted cash flows from the use of the assets. If such assets are considered to be impaired, the assets are written down to their estimated fair value. No indicators of impairment were identified for the years ended December 31, 2018, 2017 and 2016.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of our cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate fair value as of December 31, 2018 and December 31, 2017 because of the relatively short duration of these instruments. We use a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. The hierarchy requires us to use observable inputs when available, and to minimize the use of unobservable inputs when determining fair value. The three tiers are defined as follows: •Level 1. Observable inputs based on unadjusted quoted prices in active markets for identical assets or liabilities; •Level 2. Inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and •Level 3. Unobservable inputs for which there is little or no market data, which require us to develop our own assumptions.
Stock-Based Compensation	Stock-Based Compensation We account for stock-based compensation expense related to stock-based awards based on the estimated fair value of the award on the grant date. We calculate the fair value of stock options using the Black-Scholes Option Pricing Model. The fair value of RSUs is based on the closing market price of our common stock on the Nasdaq Global Market on the date of grant. For service-based awards, stock-based compensation expense is recognized on a straight-line basis over the requisite service period. For performance-based awards, stock-based compensation expense is recognized using the accelerated attribution method, based on the probability of satisfying the performance condition. For awards that contain market conditions, compensation expense is measured using a Monte Carlo simulation and recognized using the accelerated attribution method over the derived service period based on the expected market performance as of the grant date. For restricted stock units, stock-based compensation expense is recognized on a straight-line basis over the requisite service period. We account for forfeitures as they occur, rather than estimating expected forfeitures. Basic and Diluted Loss per Common Share We use the two-class method to compute net loss per common share because we have issued securities, other than common stock, that contractually entitle the holders to participate in dividends and earnings. These participating securities include our convertible preferred stock which have non-forfeitable rights to participate in any dividends declared on our common stock. The two-class method requires earnings for the period to be allocated between common stock and participating securities based upon their respective rights to receive distributed and undistributed earnings. Under the two-class method, for periods with net income, basic net income per common share is computed by dividing the net income attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Net income attributable to common stockholders is computed by subtracting from net income the portion of current year earnings that the participating securities would have been entitled to receive pursuant to their dividend rights had all of the year’s earnings been distributed. No such adjustment to earnings is made during periods with a net loss, as the holders of the participating securities have no obligation to fund losses. Diluted net income per common share is computed under the two-class method by using the weighted average number of shares of common stock outstanding, plus, for periods with net income attributable to common stockholders, the potential dilutive effects of stock options and warrants. In addition, we analyze the potential dilutive effect of the outstanding participating securities under the “if-converted” method when calculating diluted earnings per share, in which it is assumed that the outstanding participating securities convert into common stock at the beginning of the period or date of issuance, if later. We report the more dilutive of the approaches (two-class or “if-converted”) as our diluted net income per share during the period. Due to net losses for the years ended December 31, 2018, 2017 and 2016, basic and diluted net loss per share were the same, as the effect of potentially dilutive securities would have been anti-dilutive. Income Taxes We use the asset and liability method of accounting for income taxes in which deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases. We measure deferred tax assets and liabilities using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be reversed. We recognize the effect on deferred tax assets and liabilities of a change in tax rates as income and expense in the period that includes the enactment date. A valuation allowance is established if it is more likely than not that all or a portion of the deferred tax asset will not be realized. Our tax positions are subject to income tax audits by multiple tax jurisdictions throughout the world. We recognize the tax benefit of an uncertain tax position only if it is more likely than not the position is sustainable upon examination by the taxing authority. We measure the tax benefit recognized as the largest amount of benefit which is more likely than not to be realized upon settlement with the taxing authority. We recognize penalties and interest related to unrecognized tax benefits as income tax expense. We calculate the current and deferred income tax provision based on estimates and assumptions that could differ from the actual results reflected in income tax returns filed in subsequent years and record adjustments based on filed income tax returns when identified. The amount of income taxes paid is subject to examination by U.S. federal, state and foreign tax authorities. The estimate of the potential outcome of any uncertain tax issue is subject to our assessment of relevant risks, facts and circumstances existing at that time. To the extent the assessment of such tax position changes, we record the change in estimate in the period in which we make that determination. Segment Reporting Operating segments are defined as components of an enterprise for which discrete financial information is available that is evaluated regularly by the chief operating decision maker (“CODM”) for purposes of allocating resources and evaluating financial performance. Our CODM is our chief executive officer, who reviews financial information presented on a companywide basis for purposes of allocating resources and evaluating financial performance. As such, our operations constitute a single operating segment and one reportable segment. Foreign Currency Our operations located outside of the United States where the local currency is the functional currency are translated into U.S. dollars using the current rate method. Results of operations are translated at the average rate of exchange for the period. Assets and liabilities are translated at the closing rates on the balance sheet date. Gains and losses on translation of these accounts are accumulated and reported as a separate component of stockholders’ equity (deficit) and other comprehensive loss. Gains and losses on foreign currency transactions are recognized in the accompanying consolidated statements of operations as a component of other expense, net. Transaction gains and losses from transactions denominated in foreign currencies resulted in net transaction losses of $3.0 million for the year ended December 31, 2018, net transaction gains of $2.6 million for the year ended December 31, 2017 and net transaction losses of $1.5 million for the year ended December 31, 2016. Research and Development Research and development expenses include payroll, employee benefits, and other headcount-related costs associated with product development. Our product utilizes a common codebase, whether accessed by customers via the cloud or via an on-premises installation. Since our software is sold and licensed externally, we consider our software as external-use software for purposes of applying the capitalized software development guidance. Product development costs are expensed as incurred until technological feasibility has been established, which we define as the completion of all planning, designing, coding and testing activities that are necessary to establish products that meet design specifications including functions, features and technical performance requirements. We have determined that technological feasibility for our software products is reached shortly before they are released for sale. Costs incurred after technological feasibility is established are not significant, and accordingly we expense all research and development costs when incurred. Advertising We expense advertising costs as they are incurred. Advertising expenses were $3.9 million, $3.0 million and $1.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. Emerging Growth Company Status We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act (the "JOBS Act"). The JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. Thus, an emerging growth company can delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. We have elected to avail ourselves of this extended transition period and, as a result, we will not adopt new or revised accounting standards on the relevant dates on which adoption of such standards is required for other public companies.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted On December 22, 2017, the Tax Cuts and Jobs Act (the "TCJA") was enacted, substantially changing the U.S. Federal tax system. Notable provisions of the TCJA include the reduction of the corporate tax rate from 35% to 21% beginning in 2018, the imposition of a one-time transition tax on unremitted cumulative non-U.S. earnings of foreign subsidiaries, and the implementation of a territorial tax system. While the changes from the TCJA are generally effective beginning in 2018, U.S. GAAP accounting for income taxes requires the effect of a change in tax laws or rates to be recognized in income from continuing operations for the period that includes the enactment date. Due to the complexities involved in accounting for the enactment of the TCJA, the Securities and Exchange Commission Staff Accounting Bulletin No. 118 (“SAB 118”) allowed us to record provisional amounts in earnings for the year ended December 31, 2017. Where reasonable estimates can be made, the provisional accounting should be based on such estimates. When no reasonable estimate can be made, the provisional accounting may be based on the tax law in effect before the TCJA. We were required to complete our tax accounting for the TCJA in the period when we obtained, prepared, and analyzed the information to complete the income tax accounting. We completed our tax accounting for the TCJA in 2018. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting ("ASU 2017-09"), which clarifies when a change to the terms or conditions of a share-based payment award must be accounted for as a modification. ASU 2017-09 requires modification accounting if the fair value, vesting condition or the classification of the award is not the same immediately before and after a change to the terms and conditions of the award. ASU 2017-09 became effective on a prospective basis beginning on January 1, 2018. The adoption of ASU 2017-09 did not have an impact on our consolidated financial statements for the year ended December 31, 2018. Not Yet Adopted In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which provides new guidance for revenue recognition. ASU 2014-09 provides that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 also requires improved disclosures to help users of financial statements better understand the nature, amount, timing, and uncertainty of revenue that is recognized. Entities have the option of using either a full retrospective or modified retrospective approach for the adoption of the standard. In March 2016, the FASB issued ASU No. 2016-08, Principal Versus Agent Considerations (Reporting Revenue Gross Versus Net) (“ASU 2016-08”), which clarifies implementation guidance on principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Identifying Performance Obligations and Licensing (“ASU 2016-10”), which clarifies the identification of performance obligations and the licensing implementation guidance in ASU 2014-09. In addition, in May 2016, the FASB issued ASU No. 2016-12, Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), which clarifies the guidance on assessing collectibility, presentation of sales taxes, noncash consideration and completed contracts and contract modifications at transition. For public entities, the new standard is effective for annual periods and interim periods within those annual periods, beginning after December 15, 2017. For all other entities, the new standard is effective for annual periods beginning after December 15, 2018, and interim periods within those annual periods beginning after December 15, 2019. We have elected to avail ourselves of the JOBS Act extended transition period that permits us to defer adoption until January 1, 2019. In accordance with guidance, the new standard will be adopted in our Annual Report on Form 10-K for the fiscal year ending December 31, 2019 but will not be adopted in our Quarterly Reports on Form 10-Q to be filed during 2019. The ASU 2014-09 guidance allows two methods of adoption: retrospectively to each prior reporting period (full retrospective method) or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (modified retrospective method). We are going to adopt the new standard using the modified retrospective method. We do not expect the new standard to have a material impact on the timing of revenue recognition related to our cloud-based subscriptions and standalone professional services. However, we expect the new standard to have a significant impact on the timing of revenue recognition related to our on-premise term license contracts. Under current industry-specific software revenue recognition guidance, we have historically concluded that we did not have VSOE of fair value of the undelivered services related to on-premise term license contracts, and accordingly, have recognized on-premise term license contracts and related services ratably over the contract term. Under this new standard, the requirement to have VSOE for undelivered services is eliminated. Therefore, we will be required to recognize a portion of revenue from the on-premise term license contracts upon delivery of the software. In addition, we expect the new standard to impact our accounting for contract acquisition costs, both with respect to the amounts that will be capitalized as well as the period of amortization. Currently, we defer the direct and incremental commission costs to obtain a contract with a customer and amortize those costs over the term of the related customer contract consistent with the related revenue. Under the new standard, we will defer the incremental costs to obtain a contract with a customer. Therefore, the new standard will result in additional costs being capitalized, including fringe benefits. Under the new standard, initial incremental costs to obtain a contract will be amortized over the customer's estimated economic life of five years, which was calculated based on both qualitative and quantitative factors, such as product life cycles, contractual terms and customer attrition. Incremental contract costs paid relating to contract renewals will be deferred and amortized on a straight-line basis over the related renewal period. As a result, we expect the deferred commissions asset to increase and the related amortization expense in each reporting period to decrease under the new standard. We are still in the process of quantifying the effects of the adoption of ASU 2014-09 as well as continuing to evaluate the impact of the adoption of the standard on our consolidated financial statements, including our footnotes. In February 2016, the FASB issued ASU No. 2016-2, Leases (Topic 842) (“ASU 2016-2”), which requires that lessees recognize assets and liabilities for leases with lease terms greater than 12 months in the statement of financial position. ASU 2016-2 also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. The update is effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted. We are currently evaluating the impact the adoption of ASU 2016-2 will have on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326) ("ASU 2016-13"), which requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. This replaces the existing incurred loss model and is applicable to the measurement of credit losses on financial assets measured at amortized cost. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early application will be permitted for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We are currently evaluating the impact that the standard will have on our consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”), which aims to reduce the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. ASU 2016-15 will require adoption on a retrospective basis unless it is impracticable to apply, in which case we would be required to apply the amendments prospectively as of the earliest date practicable. ASU 2016-15 is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019. Early adoption is permitted. We do not expect ASU 2016-15 to have a material impact on our consolidated financial statements.

Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Schedule of Accounts, Notes, Loans and Financing Receivable

Activity within the allowance for doubtful accounts was as follows (in thousands):


	Year Ended December 31,
	2018		2017		2016
Balance as of January 1	$	400	$	400	$	400
Additions	211		62		7
Less write-offs, net of recoveries	(11)		(62)		(7)
Balance as of December 31	$	600	$	400	$	400

Property, Plant And Equipment, Useful Life


Asset Category						Useful Life (in years)
Computer software						3
Computer hardware						3
Equipment						5
Office furniture and fixtures						10
Leasehold improvements						Shorter of useful life of assets or lease term

Summary of Changes in Level 3 Instruments Measured at Fair Value On Recurring Basis

The following table presents the changes in our Level 3 instruments measured at fair value on a recurring basis during the years ended December 31, 2017 and 2016 (in thousands):


	Year Ended December 31,
	2017		2016
Balance as of January 1,	$	850	$	650
Change in fair value of warrant liability	341		200
Reclassification of warrant liability to equity	(1,191)		—
Balance as of December 31,	$	—	$	850

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax

For the years ended December 31, 2018, 2017 and 2016, our loss before income taxes was comprised of the following (in thousands):


	2018		2017		2016
Domestic	$	(30,663)	$	(23,093)	$	(4,524)
Foreign	(18,549)		(7,153)		(9,620)
Total	$	(49,212)	$	(30,246)	$	(14,144)

Schedule of Components of Income Tax Expense (Benefit)

For the years ended December 31, 2018, 2017 and 2016, our income tax expense (benefit) was comprised of the following (in thousands):


	2018		2017		2016
Current:
Federal	$	—	$	(65)	$	(627)
State	25		68		(200)
Foreign	432		1,009		266
Total current expense (benefit)	457		1,012		(561)
Deferred:
Federal	—		(42)		(922)
State	—		—		(230)
Foreign	(218)		(209)		30
Total deferred expense (benefit)	(218)		(251)		(1,122)
Total income tax expense (benefit)	$	239	$	761	$	(1,683)

Schedule of Effective Income Tax Rate Reconciliation


	2018		2017		2016
U.S. federal statutory tax rate	21.0	%	34.0	%	34.0	%
State tax expense	7.2		4.9		1.4
Foreign rate differential	(5.1)		(6.7)		(17.8)
Nondeductible expenses	(0.7)		(0.9)		(2.3)
Equity compensation	9.5		—		—
Tax credits	3.9		5.8		6.5
Unrecognized tax benefits	(0.8)		(0.7)		(0.2)
Other	0.6		(0.3)		(0.2)
Remeasurement of deferred taxes	—		(7.0)		—
Change in valuation allowance	(36.0)		(31.6)		(9.6)
Total	(0.4)	%	(2.5)	%	11.8	%

Schedule of Deferred Tax Assets and Liabilities

As of December 31, 2018 and 2017, significant components of our deferred tax assets and liabilities were as follows (in thousands):


	2018		2017
Deferred tax assets:
Net operating losses	$	21,059	$	10,413
Tax credits	5,945		4,169
Deferred revenue	4,179		1,248
Equity compensation	3,923		1,207
Accrued vacation	1,170		967
Deferred rent	373		473
Bad debt	164		109
Depreciation	151		—
Other	548		287
Gross deferred tax assets	37,512		18,873
Less: Valuation allowance	(30,039)		(12,328)
Total deferred tax assets	7,473		6,545
Deferred tax liabilities:
Prepaid expenses	(6,640)		(5,614)
Unbilled receivables	(419)		(555)
Depreciation	—		(174)
Other	(130)		(8)
Total deferred tax liabilities	(7,189)		(6,351)
Net deferred tax asset	$	284	$	194

Summary of Income Tax Contingencies

The following table summarizes the activity related to our unrecognized tax benefit from January 1, 2016 to December 31, 2018 (in thousands):


Balance as of January 1, 2016	$	384
Additions for tax positions in current years	171
Additions for tax positions in prior years	—
Reductions due to lapse in statutes of limitations	(136)
Settlements	—
Balance as of December 31, 2016	419
Additions for tax positions in current years	232
Additions for tax positions in prior years	—
Reductions due to lapse in statutes of limitations	—
Settlements	—
Balance as of December 31, 2017	651
Additions for tax positions in current years	388
Additions for tax positions in prior years	—
Reductions due to lapse in statutes of limitations	—
Settlements	—
Balance as of December 31, 2018	$	1,039

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Assumptions Used to Estimate the Fair Value of Stock Options Granted

The following table summarizes the assumptions used to estimate the fair value of stock options granted during the years ended December 31:


	2018	2017	2016
Risk-free interest rate	*	1.9% - 2.2%	1.3% - 1.5%
Expected term (in years)	*	6.5	6.5
Expected volatility	*	38.1% - 40.6%	40.9% - 42.0%
Expected dividend yield	*	—%	—%

* Not applicable because no stock options were granted during the period.

Summary of the Stock Option Activity

The following table summarizes the stock option activity for the years ended December 31, 2018 and 2017:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2017	6,784,448	$	4.65	6.5	$	44,259
Granted	1,256,200	11.92
Exercised	(876,121)	1.27			14,807
Canceled	(153,640)	7.29
Outstanding at December 31, 2017	7,010,887	6.36		6.6	176,122
Granted	—	—
Exercised	(1,486,218)	2.10			41,606
Canceled	(503,601)	9.51
Outstanding at December 31, 2018	5,021,068	7.30		6.4	97,440
Exercisable at December 31, 2018	3,448,348	6.21		5.9	70,682

Schedule of Restricted Stock Unit Activity

The following table summarizes the restricted stock unit activity for the years ended December 31, 2018 and 2017:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2017	—	$	—
Granted	738,055	22.15
Vested	(4,930)	20.24
Canceled	(1,150)	21.40
Non-vested outstanding at December 31, 2017	731,975	22.16
Granted	622,166	29.60
Vested	(143,390)	22.19
Canceled	(35,702)	23.97
Non-vested outstanding at December 31, 2018	1,175,049	26.04

Schedule of Components of Stock-based Compensation Expense

The following table summarizes the components of our stock-based compensation expense for the years ended December 31, 2018 and 2017 (in thousands):


	2018		2017
Stock-based compensation expense related to stock options	$	7,947	$	9,607
Stock-based compensation expense related to restricted stock units	7,714		753
Stock-based compensation expense related to the issuance of common stock to directors	393		222
Stock-based compensation expense related to stock option modifications	—		2,394
Total stock-based compensation expense	$	16,054	$	12,976

Schedule of Stock-based Compensation Expense Included in Condensed Consolidated Statements of Operations


	2018		2017
Cost of revenue
Subscriptions, software and support	$	514	$	575
Professional services	1,717		1,295
Operating expenses
Sales and marketing	3,473		3,233
Research and development	2,416		2,822
General and administrative	7,934		5,051
Total stock-based compensation expense	$	16,054	$	12,976

Basic and Diluted Loss per Common Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table sets forth the computation of basic and diluted net loss per share for the years ended December 31 (in thousands, except per share data):


	Year Ended December 31,
	2018		2017		2016
Numerator:
Net loss	$	(49,451)	$	(31,007)	$	(12,461)
Accretion of dividends on convertible preferred stock	—		357		857
Net loss attributable to common stockholders	$	(49,451)	$	(31,364)	$	(13,318)
Denominator
Weighted average common shares outstanding, basic and diluted	62,140,684		49,529,833		34,274,718
Net loss per share attributable to common stockholders, basic and diluted	$	(0.80)	$	(0.63)	$	(0.39)

Summary of Securities Excluded From Calculation of Weighted Average Common Shares


	Year Ended December 31,
	2018	2017	2016
Convertible preferred stock:
Series A convertible preferred stock	—	—	12,043,108
Series B convertible preferred stock	—	—	6,120,050
Warrant to purchase Series A convertible preferred stock	—	—	84,360
Stock options	5,021,068	7,010,887	6,784,448
Restricted stock units	1,175,049	731,975	—

Selected Quarterly Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information

These quarterly results are not necessarily indicative of our operating results to be expected in the future.


	Three Months Ended
	Dec 31, 2018		Sep 30, 2018		Jun 30, 2018		Mar 31, 2018		Dec 31, 2017		Sep 30, 2017		Jun 30, 2017		Mar 31, 2017
	(in thousands)
	(unaudited)
Consolidated Statements of
Operations Data:
Revenue:
Subscriptions, software and support	$	35,108	$	30,905	$	33,047	$	26,952	$	25,398	$	22,660	$	22,012	$	21,444
Professional services	25,108		24,043		26,836		24,744		25,164		21,988		21,186		16,885
Total revenue	60,216		54,948		59,883		51,696		50,562		44,648		43,198		38,329
Cost of revenue:
Subscriptions, software and support	3,284		3,261		2,824		2,628		2,488		2,341		2,488		2,062
Professional services	18,926		16,831		18,750		18,421		16,169		14,272		14,149		10,628
Total cost of revenue	22,210		20,092		21,574		21,049		18,657		16,613		16,637		12,690
Gross profit	38,006		34,856		38,309		30,647		31,905		28,035		26,561		25,639
Operating expenses:
Sales and marketing	30,177		25,467		27,384		22,964		22,463		19,725		22,775		17,003
Research and development	12,332		11,737		10,785		9,870		8,968		8,596		9,971		7,300
General and administrative	8,799		12,537		8,425		8,060		7,429		6,237		8,635		4,849
Total operating expenses	51,308		49,741		46,594		40,894		38,860		34,558		41,381		29,152
Operating loss	(13,302)		(14,885)		(8,285)		(10,247)		(6,955)		(6,523)		(14,820)		(3,513)
Other expense (income):
Other expense (income), net	510		110		2,593		(918)		(380)		(425)		(734)		(499)
Interest expense (income)	64		67		54		13		22		(2)		197		256
Total other expense (income)	574		177		2,647		(905)		(358)		(427)		(537)		(243)
Loss before income taxes	(13,876)		(15,062)		(10,932)		(9,342)		(6,597)		(6,096)		(14,283)		(3,270)
Income tax expense (benefit)	27		(34)		35		211		272		188		176		125
Net loss ⁽¹⁾⁽²⁾	$	(13,903)	$	(15,028)	$	(10,967)	$	(9,553)	$	(6,869)	$	(6,284)	$	(14,459)	$	(3,395)

(1) In the second quarter of 2017, we recorded $6.2 million of cumulative stock-based compensation expense upon the

effectiveness of our IPO and $2.4 million of stock-based compensation expense related to the stock option modifications.

See Note 7 for further discussion of stock-based compensation expense.

(2) In the third quarter of 2018, we recorded $4.5 million of cumulative stock-based compensation expense upon the

vesting of the 2016 CEO Grant. See Note 7 for further discussion of stock-based compensation expense.

Significant Accounting Policies - Additional Information (Details)	1 Months Ended			12 Months Ended
	Aug. 31, 2018 USD ($) $ / shares shares	Nov. 30, 2017 $ / shares shares	May 31, 2017 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) agency	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Proceeds from initial public offering, net of underwriting discounts				$ 0	$ 80,213,000	$ 0
Deferred offering costs				$ 2,400,000
Percentage of license revenue				2.00%	1.00%
Tenant improvement allowance receivable				$ 14,400,000	$ 0
Change in allowance for doubtful accounts				0
Commission expense				15,600,000	11,800,000	6,500,000
Foreign currency transactions, gains and (losses)				(3,000,000.0)	2,600,000	(1,500,000)
Advertising expense				$ 3,900,000	$ 3,000,000.0	$ 1,400,000
Customer Concentration Risk \| Sales Revenue, Net \| Foreign Customers
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage				28.70%	27.00%	19.50%
Customer Concentration Risk \| Sales Revenue, Net \| Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage				15.70%	15.40%	26.20%
Customer Concentration Risk \| Sales Revenue, Net \| Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage				7.80%	8.40%	17.70%
Number of federal government agencies \| agency				3
Minimum
Summary Of Significant Accounting Policies [Line Items]
SaaS Subscriptions contracts term				1 year
Term license subscription contracts term				1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
SaaS Subscriptions contracts term				5 years
Term license subscription contracts term				5 years
Class A Common Stock
Summary Of Significant Accounting Policies [Line Items]
Number of shares issued in public offering (in shares) \| shares	2,000,000
Sale of stock, offering price (in usd per share) \| $ / shares	$ 35.15
Proceeds from initial public offering, net of underwriting discounts			$ 77,800,000
Number of shares issued by the company in public offering (in shares) \| shares	1,675,000
Number of shares issued by sharesholders in public offering (in shares) \| shares	325,000
Net proceeds from public offering	$ 57,800,000
Secondary Offering \| Class A Common Stock
Summary Of Significant Accounting Policies [Line Items]
Number of shares issued in public offering (in shares) \| shares		4,370,000
Sale of stock, offering price (in usd per share) \| $ / shares		$ 20.25
IPO \| Class A Common Stock
Summary Of Significant Accounting Policies [Line Items]
Number of shares issued in public offering (in shares) \| shares			7,187,500
Sale of stock, offering price (in usd per share) \| $ / shares			$ 12.00
Computer software
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life				3 years
Computer hardware
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life				3 years
Equipment
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life				5 years
Office furniture and fixtures
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life				10 years

Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance as of January 1	$ 400	$ 400	$ 400
Additions	211	62	7
Less write-offs, net of recoveries	11	62	7
Balance as of December 31	$ 600	$ 400	$ 400

Significant Accounting Policies - Summary of Changes in Level 3 Instruments Measured at Fair Value On Recurring Basis (Detail) - Fair Value, Measurements, Recurring - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of January 1,	$ 850	$ 650
Change in fair value of warrant liability	341	200
Reclassification of warrant liability to equity	(1,191)	0
Balance as of December 31,	$ 0	$ 850

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,007	$ 8,238
Less: accumulated depreciation	(7,468)	(5,575)
Property and equipment, net	7,539	2,663
Depreciation and amortization expense	2,000	900	$ 800
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	9,958	4,226
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,535	1,644
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,727	1,727
Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	649	510
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 138	$ 131

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued contract labor costs	$ 3,128	$ 3,424
Accrued third party license fees	729	235
Accrued hosting costs	579	466
Accrued reimbursable employee expenses	459	286
Accrued audit and tax expenses	375	248
Accrued marketing and tradeshow expenses	229	128
Other accrued expenses	1,965	1,680
Total	$ 7,464	$ 6,467

Debt - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Nov. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 30, 2017
Line of Credit Facility [Line Items]
Loss on extinguishment of debt		$ 0	$ (384,000)	$ 0
Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility	$ 20,000,000.0				$ 5,000,000.0
Term Loan
Line of Credit Facility [Line Items]
Credit facility					20,000,000.0
Line of credit, outstanding borrowings		0
Term Loan \| Other (Income) Expense
Line of Credit Facility [Line Items]
Loss on extinguishment of debt		$ (400,000)
Subordinated Term Loan
Line of Credit Facility [Line Items]
Credit facility					$ 10,000,000.0
Minimum
Line of Credit Facility [Line Items]
Unused facility fee, revolving line of credit	0.15%
Adjusted quick ratio	135.00%
Minimum \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Additional interest rate margin	2.00%
Minimum \| Prime Rate
Line of Credit Facility [Line Items]
Additional interest rate margin	1.00%
Maximum
Line of Credit Facility [Line Items]
Unused facility fee, revolving line of credit	0.25%
Maximum \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Additional interest rate margin	2.50%
Maximum \| Prime Rate
Line of Credit Facility [Line Items]
Additional interest rate margin	1.50%

Income Taxes - Net Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Domestic									$ (30,663)	$ (23,093)	$ (4,524)
Foreign									(18,549)	(7,153)	(9,620)
Loss before income taxes	$ (13,876)	$ (15,062)	$ (10,932)	$ (9,342)	$ (6,597)	$ (6,096)	$ (14,283)	$ (3,270)	$ (49,212)	$ (30,246)	$ (14,144)

Income Taxes - Schedule of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal									$ 0	$ (65)	$ (627)
State									25	68	(200)
Foreign									432	1,009	266
Total current expense (benefit)									457	1,012	(561)
Deferred:
Federal									0	(42)	(922)
State									0	0	(230)
Foreign									(218)	(209)	30
Total deferred expense (benefit)									(218)	(251)	(1,122)
Total income tax expense (benefit)	$ 27	$ (34)	$ 35	$ 211	$ 272	$ 188	$ 176	$ 125	$ 239	$ 761	$ (1,683)

Income Taxes - Schedule of Reconciliation of Statutory to Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	21.00%	34.00%	34.00%
State tax expense	7.20%	4.90%	1.40%
Foreign rate differential	(5.10%)	(6.70%)	(17.80%)
Nondeductible expenses	(0.70%)	(0.90%)	(2.30%)
Equity compensation	9.50%	0.00%	0.00%
Tax credits	3.90%	5.80%	6.50%
Unrecognized tax benefits	(0.80%)	(0.70%)	(0.20%)
Other	0.60%	(0.30%)	(0.20%)
Remeasurement of deferred taxes	0.00%	(7.00%)	0.00%
Change in valuation allowance	(36.00%)	(31.60%)	(9.60%)
Total	(0.40%)	(2.50%)	11.80%

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating losses	$ 21,059	$ 10,413
Tax credits	5,945	4,169
Deferred revenue	4,179	1,248
Equity compensation	3,923	1,207
Accrued vacation	1,170	967
Deferred rent	373	473
Bad debt	164	109
Depreciation	151	0
Other	548	287
Gross deferred tax assets	37,512	18,873
Less: Valuation allowance	(30,039)	(12,328)
Total deferred tax assets	7,473	6,545
Deferred tax liabilities:
Deferred Tax Liabilities, Prepaid Expenses	(6,640)	(5,614)
Unbilled receivables	(419)	(555)
Depreciation	0	(174)
Other	(130)	(8)
Total deferred tax liabilities	(7,189)	(6,351)
Net deferred tax asset	$ 284	$ 194

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Beginning balance	$ 651	$ 419	$ 384
Additions for tax positions in current years	388	232	171
Additions for tax positions in prior years	0	0	0
Reductions due to lapse in statutes of limitations	0	0	(136)
Settlements	0	0	0
Ending balance	$ 1,039	$ 651	$ 419

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, state, tax effected	$ 3,700	$ 1,600
Net change in total valuation allowance	17,700
Valuation allowance against foreign deferred tax assets	30,039	12,328
Recognized interest and penalties related to uncertain tax positions		2	$ 2
Cumulative balance of interest and penalties related to uncertain tax positions	33
Unrecognized tax benefits, portion affecting tax rate	1,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	56,900	25,300
Federal tax credit carryforwards	6,400	4,500
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	57,200	25,300
Swiss Federal Tax Administration (FTA) \| Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	56,300	$ 35,700
Valuation allowance against foreign deferred tax assets	$ 5,300

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended	12 Months Ended
	Apr. 25, 2017	Nov. 30, 2018	May 31, 2017	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period for option exercise					5 years
Stock-based compensation expense					$ 16,054	$ 12,976
Canceled shares pursuant to Agreement (in shares)					503,601	153,640
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)					622,166	738,055
Granted (in usd per share)					$ 29.60	$ 22.15
Stock-based compensation expense related to restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 6,200
Stock-based compensation expense related to restricted stock units \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 6,200
Stock Option Modifications
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,400			$ 2,400	$ 0	$ 2,394
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available to be issued					5,680,655
2017 Equity Incentive Plan \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		255,930
Granted (in usd per share)		$ 30.06
Value of awards at grant date		$ 7,700
2017 Equity Incentive Plan \| Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available to be issued			6,421,442		7,040,863
2007 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available to be issued			421,442
Number of shares available for grants			0
Period for which options can be granted					10 years

Stock-Based Compensation - Summary of Estimate the Fair Value of Stock Options Granted (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Goods and Nonemployee Services Transaction [Line Items]
Expected term (in years)	6 years 6 months	6 years 6 months
Expected dividend yield	0.00%	0.00%
Minimum
Share-based Goods and Nonemployee Services Transaction [Line Items]
Risk-free interest rate	1.90%	1.30%
Expected volatility	38.10%	40.90%
Maximum
Share-based Goods and Nonemployee Services Transaction [Line Items]
Risk-free interest rate	2.20%	1.50%
Expected volatility	40.60%	42.00%

Stock-Based Compensation - Summary of the Stock Option Activity (Detail) - USD ($)		1 Months Ended		3 Months Ended		12 Months Ended
	Apr. 25, 2017	Dec. 31, 2018	Jul. 31, 2016	Sep. 30, 2018	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Beginning balance						7,010,887	6,784,448
Granted (in shares)						0	1,256,200
Exercised (in shares)						(1,486,218)	(876,121)
Canceled (in shares)						(503,601)	(153,640)
Ending balance		5,021,068				5,021,068	7,010,887	6,784,448
Exercisable at December 31, 2018		3,448,348				3,448,348
Weighted Average Exercise Price
Beginning balance						$ 6.36	$ 4.65
Granted (in usd per share)						0	11.92
Exercised (in usd per share)						2.10	1.27
Canceled (in usd per share)						9.51	7.29
Ending balance		$ 7.30				7.30	$ 6.36	$ 4.65
Exercisable at December 31, 2018		$ 6.21				$ 6.21
Weighted Average Remaining Contractual Term (Years)
Beginning balance						6 years 4 months 24 days	6 years 7 months 6 days	6 years 6 months
Ending balance						6 years 4 months 24 days	6 years 7 months 6 days	6 years 6 months
Exercisable at December 31, 2018						5 years 10 months 24 days
Aggregate Intrinsic Value (in thousands)
Beginning balance						$ 176,122,000	$ 44,259,000
Exercised						41,606,000	14,807,000
Ending balance		$ 97,440,000				97,440,000	$ 176,122,000	$ 44,259,000
Exercisable at December 31, 2018		70,682,000				70,682,000
Weighted average grant-date fair value of options granted (in usd per share)							$ 5.05	$ 4.35
Total fair value of stock options vested						10,500,000	$ 5,600,000
Total compensation cost related to unvested stock options not yet recognized		$ 2,600,000				$ 2,600,000
Weighted average period, unvested stock options						2 years 1 month 6 days
Stock options issued to purchase common stock (in shares)	216,160
Stock options granted to CEO (in shares)						0	1,256,200
Stock-based compensation expense						$ 16,054,000	$ 12,976,000
Stock Option Modifications
Aggregate Intrinsic Value (in thousands)
Stock-based compensation expense	$ 2,400,000				$ 2,400,000	$ 0	2,394,000
2007 Stock Option Plan \| Chief Executive Officer
Number of Shares
Granted (in shares)			1,828,080			1,828,080
Canceled (in shares)		(383,897)
Weighted Average Exercise Price
Exercised (in usd per share)			$ 9.46
Aggregate Intrinsic Value (in thousands)
Stock options granted to CEO (in shares)			1,828,080			1,828,080
Stock-based compensation expense				$ 4,500,000		$ 5,600,000	$ 2,700,000

Stock-Based Compensation - Schedule of Restricted Stock Unit Activity (Details) - Restricted stock units - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Non-vested outstanding, beginning balance (in shares)	731,975	0
Granted (in shares)	622,166	738,055
Vesting of restricted stock units (in shares)	(143,390)	(4,930)
Canceled (in shares)	(35,702)	(1,150)
Non-vested outstanding, ending balance (in shares)	1,175,049	731,975
Weighted Average Grant Date Fair Value
Non-vested outstanding, beginning balance (in usd per share)	$ 22.16	$ 0
Granted (in usd per share)	29.60	22.15
Vested (in usd per share)	22.19	20.24
Canceled (in usd per share)	23.97	21.40
Non-vested outstanding, ending balance (in usd per share)	$ 26.04	$ 22.16
Total unrecognized compensation cost related to unvested restricted stock units	$ 25.4
Weighted average remaining vesting period	2 years

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Apr. 25, 2017	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense			$ 16,054	$ 12,976
Stock options
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense			7,947	9,607
Stock-based compensation expense related to restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense			7,714	753
Stock-based compensation expense related to the issuance of common stock to directors
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense			393	222
Stock-based compensation expense related to stock options
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,400	$ 2,400	$ 0	$ 2,394

Stock-Based Compensation - Schedule of Stock-based Compensation Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 16,054	$ 12,976
Subscriptions, software and support
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	514	575
Professional services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,717	1,295
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	3,473	3,233
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	2,416	2,822
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 7,934	$ 5,051

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) vote $ / shares shares	Dec. 31, 2017 $ / shares shares	May 31, 2017 shares
Class of Stock [Line Items]
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001
Warrant exercise price (in dollars per share) \| $ / shares	$ 0.88905
Warrants outstanding (in shares)	0	0
Series A convertible preferred stock
Class of Stock [Line Items]
Warrant to purchase shares of preferred stock (in shares)	84,360
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued (in shares)	29,626,054	13,030,081
Common stock, shares outstanding (in shares)	29,626,054	13,030,081
Number of votes entitled to stockholders \| vote	1
Conversion of stock (in shares)	1
Maximum percentage of aggregate voting power of capital stock which triggers conversion of stock	10.00%
Class B Common Stock
Class of Stock [Line Items]
Conversion of convertible preferred stock to common stock (in shares)	18,163,158
Convertible preferred stock outstanding shares converted into common stock (in shares)	1
Preferred stock conversion basis	one
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued (in shares)	34,290,383	47,569,796
Common stock, shares outstanding (in shares)	34,290,383	47,569,796
Number of votes entitled to stockholders \| vote	10
Shares issued on cashless exercise of warrants (in shares)			79,363
Prior to IPO \| Class B Common Stock
Class of Stock [Line Items]
Warrant to purchase shares of preferred stock (in shares)	84,360
Warrant
Class of Stock [Line Items]
Fair value of warrant \| $	$ 1.2

Basic and Diluted Loss per Common Share - Computation of Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net loss	$ (13,903)	$ (15,028)	$ (10,967)	$ (9,553)	$ (6,869)	$ (6,284)	$ (14,459)	$ (3,395)	$ (49,451)	$ (31,007)	$ (12,461)
Accretion of dividends on convertible preferred stock									0	357	857
Net loss attributable to common stockholders									$ (49,451)	$ (31,364)	$ (13,318)
Denominator
Weighted average common shares outstanding, basic and diluted (in shares)									62,140,684	49,529,833	34,274,718
Net loss per share attributable to common stockholders, basic and diluted (in usd per share)									$ (0.80)	$ (0.63)	$ (0.39)

Basic and Diluted Loss per Common Share - Summary of Securities Excluded From Calculation of Weighted Average Common Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Series A convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	0	0	12,043,108
Series B convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	0	0	6,120,050
Warrant to purchase Series A convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	0	0	84,360
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	5,021,068	7,010,887	6,784,448
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	1,175,049	731,975	0

Commitments and Contingencies - Summary of Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Apr. 30, 2018
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Total		$ 87,200
Office Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 6,985
2020	6,371
2021	8,331
2022	6,939
2023	6,987
Thereafter	65,151
Total	100,764
Total	100,764
Equipment Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	216
2020	22
2021	0
2022	0
2023	0
Thereafter	0
Total	238
Total	238
Lease Related Commitments
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	29,587
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total	29,587
Tenant Improvement Allowance	14,441
Total	$ 15,146

Commitments and Contingencies -Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 30, 2018
Debt Instrument [Line Items]
Total payments committed under lease amount				$ 87.2
Tenant improvement allowance	$ 18.4
Deferred rent credit, current	1.2
Deferred rent, net of current portion	14.4
Deferred rent, noncurrent	17.4	$ 2.0
Total rent and lease expense	8.8	7.0	$ 6.6
Payment of royalty fees	0.3
Outstanding letters of credit	$ 10.5	$ 1.1
Letter of Credit
Debt Instrument [Line Items]
Long-term debt				$ 9.4

Segment and Geographic Information - Summary of Revenues By Geography (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 226,743	$ 176,737	$ 132,923
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	161,716	128,997	107,069
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 65,027	$ 47,740	$ 25,854

Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
Retirement Plans (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Eligibility to participate, days of service	45 days
Eligibility to participate, years of age	21 years
Maximum annual contributions per employee	75.00%
Vesting percentage of employer contribution	25.00%
Vesting term of employer contribution	4 years
Contribution expense related to employer matching contributions	$ 4.7	$ 3.3	$ 2.6
Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution expense related to employer matching contributions	$ 1.3	$ 0.9	$ 0.7

Selected Quarterly Information (Unaudited) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Apr. 25, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Total revenue		$ 60,216	$ 54,948	$ 59,883	$ 51,696	$ 50,562	$ 44,648	$ 43,198	$ 38,329	$ 226,743	$ 176,737	$ 132,923
Cost of revenue:
Total cost of revenue		22,210	20,092	21,574	21,049	18,657	16,613	16,637	12,690	84,925	64,597	50,123
Gross profit		38,006	34,856	38,309	30,647	31,905	28,035	26,561	25,639	141,818	112,140	82,800
Operating expenses:
Sales and marketing		30,177	25,467	27,384	22,964	22,463	19,725	22,775	17,003	105,992	81,966	54,137
Research and development		12,332	11,737	10,785	9,870	8,968	8,596	9,971	7,300	44,724	34,835	22,994
General and administrative		8,799	12,537	8,425	8,060	7,429	6,237	8,635	4,849	37,821	27,150	17,039
Total operating expenses		51,308	49,741	46,594	40,894	38,860	34,558	41,381	29,152	188,537	143,951	94,170
Operating loss		(13,302)	(14,885)	(8,285)	(10,247)	(6,955)	(6,523)	(14,820)	(3,513)	(46,719)	(31,811)	(11,370)
Other expense (income):
Other expense (income), net		510	110	2,593	(918)	(380)	(425)	(734)	(499)	2,295	(2,038)	1,792
Interest expense (income)		64	67	54	13	22	(2)	197	256	198	473	982
Total other expense (income)		574	177	2,647	(905)	(358)	(427)	(537)	(243)	2,493	(1,565)	2,774
Loss before income taxes		(13,876)	(15,062)	(10,932)	(9,342)	(6,597)	(6,096)	(14,283)	(3,270)	(49,212)	(30,246)	(14,144)
Income tax expense (benefit)		27	(34)	35	211	272	188	176	125	239	761	(1,683)
Net loss		(13,903)	(15,028)	(10,967)	(9,553)	(6,869)	(6,284)	(14,459)	(3,395)	(49,451)	(31,007)	(12,461)
Stock-based compensation expense										16,054	12,976
Stock-based compensation expense related to restricted stock units
Other expense (income):
Stock-based compensation expense								6,200
Stock Option Modifications
Other expense (income):
Stock-based compensation expense	$ 2,400							2,400		0	2,394
Subscriptions, software and support
Revenue:
Total revenue		35,108	30,905	33,047	26,952	25,398	22,660	22,012	21,444	126,012	91,514	69,972
Cost of revenue:
Total cost of revenue		3,284	3,261	2,824	2,628	2,488	2,341	2,488	2,062	11,997	9,379	7,437
Professional services
Revenue:
Total revenue		25,108	24,043	26,836	24,744	25,164	21,988	21,186	16,885	100,731	85,223	62,951
Cost of revenue:
Total cost of revenue		$ 18,926	16,831	$ 18,750	$ 18,421	$ 16,169	$ 14,272	$ 14,149	$ 10,628	72,928	55,218	$ 42,686
Chief Executive Officer \| 2007 Stock Option Plan
Other expense (income):
Stock-based compensation expense			$ 4,500							$ 5,600	$ 2,700

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2018
Accounting Policies [Abstract]
Organization and Description of Business	Organization and Description of BusinessAppian Corporation (together with its subsidiaries, “Appian,” the “Company,” “we” or “our”) provides a low-code software development platform that allows companies to rapidly build powerful business applications. The applications created on our platform help companies drive digital transformation and competitive differentiation. We were incorporated in the state of Delaware in August 1999. We are headquartered in Reston, Virginia and operate in Canada, Switzerland, the United Kingdom, France, Germany, the Netherlands, Italy, Australia, Spain, Singapore and Sweden.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsIn preparing our consolidated financial statements, we evaluated subsequent events through February 21, 2019, which is the date that the consolidated financial statements were available to be issued.