Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2018	Oct. 29, 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	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Trading Symbol	APPN
Class A Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		28,123,250
Class B Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		35,547,717

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 107,266	$ 73,758
Accounts receivable, net of allowance of $400	62,464	55,315
Deferred commissions, current	12,366	9,117
Prepaid expenses and other current assets	6,004	7,032
Total current assets	188,100	145,222
Property and equipment, net	3,291	2,663
Deferred commissions, net of current portion	14,658	12,376
Deferred tax assets	246	281
Other assets	569	510
Total assets	206,864	161,052
Current liabilities
Accounts payable	6,616	5,226
Accrued expenses	6,598	6,467
Other current liabilities	902	1,182
Total current liabilities	110,693	95,115
Accrued compensation and related benefits	13,528	12,075
Deferred revenue, current	83,049	70,165
Deferred tax liabilities	5	87
Deferred revenue, net of current portion	13,758	18,922
Other long-term liabilities	592	1,404
Total liabilities	125,048	115,528
Stockholders’ equity
Additional paid-in capital	212,971	141,268
Accumulated other comprehensive income	576	439
Accumulated deficit	(131,737)	(96,189)
Total stockholders’ equity	81,816	45,524
Total liabilities and stockholders’ equity	206,864	161,052
Class A Common Stock
Stockholders’ equity
Common stock	3	1
Class B Common Stock
Stockholders’ equity
Common stock	$ 3	$ 5

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 400	$ 400
Common stock, par value	$ 0.0001
Class A Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	28,036,799	13,030,081
Common stock, shares outstanding	28,036,799	13,030,081
Class B Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	35,551,517	47,569,796
Common stock, shares outstanding	35,551,517	47,569,796

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Total revenue	$ 54,948	$ 44,648	$ 166,527	$ 126,175
Cost of revenue:
Total cost of revenue	20,092	16,613	62,715	45,940
Gross profit	34,856	28,035	103,812	80,235
Operating expenses:
Sales and marketing	25,467	19,725	75,815	59,503
Research and development	11,737	8,596	32,392	25,867
General and administrative	12,537	6,237	29,022	19,721
Total operating expenses	49,741	34,558	137,229	105,091
Operating loss	(14,885)	(6,523)	(33,417)	(24,856)
Other expense (income):
Other expense (income), net	110	(425)	1,785	(1,658)
Interest expense (income)	67	(2)	134	451
Total other expense (income)	177	(427)	1,919	(1,207)
Net loss before income taxes	(15,062)	(6,096)	(35,336)	(23,649)
Income tax (benefit) expense	(34)	188	212	489
Net loss	(15,028)	(6,284)	(35,548)	(24,138)
Accretion of dividends on convertible preferred stock	0	0	0	357
Net loss attributable to common stockholders	$ (15,028)	$ (6,284)	$ (35,548)	$ (24,495)
Net loss per share attributable to common stockholders:
Basic and diluted (in dollar per share)	$ (0.24)	$ (0.10)	$ (0.58)	$ (0.53)
Weighted average common shares outstanding:
Basic and diluted (in shares)	62,480,927	60,204,596	61,583,610	45,855,044
Subscriptions, Software, And Support
Revenue:
Total revenue	$ 30,905	$ 22,660	$ 90,904	$ 66,116
Cost of revenue:
Total cost of revenue	3,261	2,341	8,713	6,891
Professional Services
Revenue:
Total revenue	24,043	21,988	75,623	60,059
Cost of revenue:
Total cost of revenue	$ 16,831	$ 14,272	$ 54,002	$ 39,049

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (15,028)	$ (6,284)	$ (35,548)	$ (24,138)
Comprehensive loss, net of income taxes:
Foreign currency translation adjustment	(400)	517	137	(879)
Total other comprehensive loss, net of income taxes	$ (15,428)	$ (5,767)	$ (35,411)	$ (25,017)

CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		60,599,877
Beginning balance at Dec. 31, 2017	$ 45,524	$ 6	$ 141,268	$ 439	$ (96,189)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(35,548)				(35,548)
Issuance of common stock from public offering, net of issuance costs (in shares)		1,675,000
Issuance of common stock from public offering, net of issuance costs	$ 57,829	$ 0	57,829	0	0
Issuance of common stock to directors (in shares)		9,160
Vesting of restricted stock units (in shares)	6,300
Exercise of stock options (in shares)	1,297,979	1,297,979
Exercise of stock options	$ 2,627		2,627
Stock-based compensation expense	11,247		11,247
Other comprehensive income	137			137
Ending balance (in shares) at Sep. 30, 2018		63,588,316
Ending balance at Sep. 30, 2018	$ 81,816	$ 6	$ 212,971	$ 576	$ (131,737)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (35,548)	$ (24,138)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,452	673
Gain on disposal of equipment	(4)	0
Bad debt expense	2	0
Deferred income taxes	69	(91)
Stock-based compensation	11,247	10,919
Fair value adjustment for warrant liability	0	341
Loss on extinguishment of debt	0	384
Changes in assets and liabilities:
Accounts receivable	(6,226)	4,329
Prepaid expenses and other assets	76	(3,184)
Deferred commissions	(5,531)	(1,056)
Accounts payable and accrued expenses	1,255	1,202
Accrued compensation and related benefits	1,814	(339)
Other current liabilities	376	(75)
Deferred revenue	7,862	1,043
Other long-term liabilities	(797)	(143)
Net cash used in operating activities	(23,953)	(10,135)
Cash flows from investing activities:
Purchases of property and equipment	(2,187)	(295)
Proceeds from sale of equipment	4	0
Net cash used in investing activities	(2,183)	(295)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting discounts	0	80,213
Proceeds from public offering, net of underwriting discounts	58,258	0
Payment of costs related to public offerings	(353)	(2,424)
Payment of dividend to Series A preferred stockholders	0	(7,565)
Proceeds from exercise of common stock options	2,627	664
Proceeds from issuance of long-term debt, net of debt issuance costs	0	19,616
Repayment of long-term debt	0	(40,000)
Net cash provided by financing activities	60,532	50,504
Effect of foreign exchange rate changes on cash and cash equivalents	(888)	1,072
Net increase in cash and cash equivalents	33,508	41,146
Cash and cash equivalents, beginning of period	73,758	31,143
Cash and cash equivalents, end of period	107,266	72,289
Supplemental disclosure of cash flow information:
Cash paid for interest	34	0
Cash paid for income taxes	178	484
Supplemental disclosure of non-cash financing activities:
Accretion of dividends on convertible preferred stock	0	357
Offering costs included in accounts payable and accrued expenses	76	0
Conversion of convertible preferred stock to common stock
Supplemental disclosure of non-cash financing activities:
Conversion of convertible preferred stock	0	48,207
Conversion of convertible preferred stock warrant to common stock warrant
Supplemental disclosure of non-cash financing activities:
Conversion of convertible preferred stock	$ 0	$ 1,191

Organization and Description of Business	9 Months Ended
Organization and Description of Business	Sep. 30, 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 software development platform that combines intelligent automation and enterprise low-code development to rapidly deliver 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.

Significant Accounting Policies

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements and footnotes have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as contained in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (the “Codification” or “ASC”) for interim financial information. In the opinion of management, the interim financial information includes all adjustments of a normal recurring nature necessary for a fair presentation of the results of operations, financial position, changes in stockholders’ equity and cash flows. The results of operations for the current period are not necessarily indicative of the results for the full year or the results for any future periods. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2017, filed with the Securities and Exchange Commission (the “SEC”) on February 23, 2018.

Use of Estimates

The preparation of our condensed consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and judgments that affect the amounts reported in these condensed 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 condensed 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 condensed consolidated financial statements include the accounts of Appian and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

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 an offering price to the public of $35.15 per share. Our net proceeds from the offering was $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 general 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. As a result, revenue from our perpetual software licenses during the three months ended September 30, 2018 was less than 1.0% of our total revenue. However, during the nine months ended September 30, 2018, we sold a $4.4 million perpetual software license to the U.S. Air Force. Therefore, revenue from our perpetual software licenses was 2.7% of our total revenue for the nine months ended September 30, 2018. Revenue from our perpetual software licenses was less than 1.0% of our total revenue for the three and nine months ended September 30, 2017.

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. Cash deposits may be in excess of insured limits. 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 14.1% and 16.1% of our revenue for the three and nine months ended September 30, 2018, respectively, of which the top three federal government agencies generated 7.2% and 8.7% of our revenue for the three and nine months ended September 30, 2018, respectively. Additionally, 29.1% and 30.0% of our revenue during the three and nine months ended September 30, 2018, respectively, was generated from foreign customers. Revenue generated from government agencies represented 14.2% and 15.4% of our revenue for the three and nine months ended September 30, 2017, respectively, of which the top three federal government agencies generated 7.7% and 9.1% of our revenue for the three and nine months ended September 30, 2017, respectively. Additionally, 28.6% and 25.6% of our revenue during the three and nine months ended September 30, 2017, respectively, was generated from foreign customers.

One customer accounted for 3.7% of accounts receivable at September 30, 2018 and a different customer accounted for 7.0% of accounts receivable at December 31, 2017.

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. There was no change in the allowance for doubtful accounts from December 31, 2017 to September 30, 2018.

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 condensed consolidated statements of operations. Commission expense was $4.0 million and $10.2 million for the three and nine months ended September 30, 2018, respectively. Commission expense was $3.2 million and $8.5 million for the three and nine months ended September 30, 2017, respectively.

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 September 30, 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 changes in our Level 3 instruments measured at fair value on a recurring basis during the three and nine months ended September 30, 2018 or the three months ended September 30, 2017.

The following table presents the changes in our Level 3 instruments measured at fair value on a recurring basis during the nine months ended September 30, 2017 (in thousands):


	Nine Months Ended
	September 30, 2017
Balance as of January 1	$	850
Change in fair value of warrant liability	341
Reclassification of warrant liability to equity	(1,191)
Balance as of September 30	$	—

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 Options Pricing Model. 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 model 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.

Emerging Growth Company Status

We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act (“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 SEC 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 are required to complete our tax accounting for the TCJA in the period when we have obtained, prepared, and analyzed the information to complete the income tax accounting. We have not completed our accounting for the tax effects of enactment of the TCJA; however, we have made reasonable estimates of the effects of the TCJA on our consolidated financial statements which are included as a component of income tax expense.

In March 2018, the FASB issued Accounting Standards Update No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 ("ASU 2018-05"), which allowed SEC registrants to record provisional amounts in earnings for the year ended December 31, 2017 due to the complexities involved in accounting for the enactment of the TCJA. In accordance with SAB No. 118, we recognized the estimated income tax effects of the TCJA in the consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2017, filed with the SEC on February 23, 2018. See Note 5 for further information regarding the provisional amounts recorded as of December 31, 2017.

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 three and nine months ended September 30, 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 intend to avail ourselves of the JOBS Act extended transition period that permits us to defer adoption until January 1, 2019.

The Topic 606 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 currently plan 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 may 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 since having a direct relationship with a contract is no longer required. 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 Topic 606 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. 2016-02, Leases (Topic 842) (“ASU 2016-02”), 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 2016-02 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 are currently in the process of evaluating the impact of adoption of this standard on our consolidated financial statements.

In February 2018, the FASB issued ASU No. 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income ("ASU 2018-02"), which provides entities the option to reclassify to retained earnings tax effects related to items in accumulated other comprehensive income ("OCI") that the FASB refers to as having been stranded in accumulated OCI as a result of tax reform. ASU 2018-02 is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. We do not expect ASU 2018-02 to have a material impact on our consolidated financial statements.

Debt	9 Months Ended
Debt	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt 2017 Financing Facility In April 2017, we entered into a new 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, the 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 our new financing facility, the lender waived the prepayment fee associated with our prior line of credit. In June 2017, we used proceeds from our initial public offering ("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 condensed 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 September 30, 2018. As of September 30, 2018, we had no outstanding borrowings under the revolving line of credit.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The provision for income taxes is based upon the estimated annual effective tax rates for the year applied to the current period income before tax plus the tax effect of any significant unusual items, discrete events or changes in tax law. Our operating subsidiaries are exposed to statutory effective tax rates ranging from zero to approximately 33%. Fluctuations in the distribution of pre-tax income among our operating subsidiaries can lead to fluctuations of the effective tax rate in the condensed consolidated financial statements. For the three and nine months ended September 30, 2018, the actual effective tax rates were 0.2% and (0.6)%, respectively. For the three and nine months ended September 30, 2017, the actual effective tax rates were (3.1)% and (2.1)%, respectively. We assess uncertain tax positions in accordance with Accounting Standards Codification 740-10, Accounting for Uncertainties in Income Taxes. As of September 30, 2018, our net unrecognized tax benefits totaled $0.7 million, of which the entire portion would favorably impact our effective tax rate in the period if recognized. We anticipate that the amount of reasonably possible unrecognized tax benefits that could decrease over the next 12 months due to the expiration of certain statutes of limitations and settlement of tax audits is not material to our consolidated financial statements. We file income tax returns in the United States federal jurisdiction and in many states and foreign jurisdictions. The tax years 2014 through 2017 remain open to examination by the major taxing jurisdictions to which we are subject. We are not currently under examination by the Internal Revenue Service for any open tax years. 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. 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 are required to complete our tax accounting for the TCJA in the period when we have obtained, prepared, and analyzed the information to complete the income tax accounting. During the three and nine months ended September 30, 2018, there were no changes made to the provisional amounts recognized in 2017. We will continue to analyze the effects of the TCJA on our financial statements. Additional impacts from the enactment of the TCJA will be recorded as they are identified during the measurement period as provided for in SAB 118, which extends up to one year from the enactment date. The final impact of the TCJA may differ from the provisional amounts that have been recognized, possibly materially, due to, among other things, changes in our interpretation of the TCJA, legislative or administrative actions to clarify the intent of the statutory language provided that differ from our current interpretation, any changes in accounting standards for income taxes or related interpretations in response to the TCJA, or any updates or changes to estimates utilized to calculate the impacts, including changes to current year earnings estimates and applicable foreign exchange rates.

Stock-Based Compensation

9 Months Ended

Sep. 30, 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”), which became effective as of the date of the final prospectus for our IPO. 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 September 30, 2018, there were 6,607,686 shares of Class A common stock reserved for issuance under the 2017 Plan, of which 5,540,439 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 5 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 effectiveness 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 Options 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 three and nine months ended September 30, 2018 and 2017:


	Three Months Ended September 30,			Nine Months Ended September 30,
	2018	2017	2018	2017
Risk-free interest rate	*	1.9% - 2.1%	*	1.9% - 2.2%
Expected term (in years)	*	6.5	*	6.5
Expected volatility	*	38.6%	*	38.6% - 40.6%
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 nine months ended September 30, 2018:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
January 1, 2018	7,010,887	$	6.36	6.6	$	176,122
Granted	—	—
Exercised	(1,297,979)	2.01			36,911
Canceled	(70,424)	9.34
Outstanding at September 30, 2018	5,642,484	7.32		6.6	145,456
Exercisable at September 30, 2018	3,905,924	6.37		6.1	104,395

The weighted average grant-date fair value of stock options granted during the nine months ended September 30, 2017 was $5.04 per share. No stock options were granted during the nine months ended September 30, 2018. The total fair value of stock options that vested during the nine months ended September 30, 2018 and 2017 was $10.2 million and $5.3 million, respectively. As of September 30, 2018, the total compensation cost related to unvested stock options not yet recognized was $3.2 million, which will be recognized over a weighted average period of 2.2 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 approach.

During the three months ended September 30, 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 the $4.7 million and $5.6 million for the three and nine months ended September 30, 2018, respectively. Stock-based compensation expense recognized for the 2016 CEO Grant was $0.5 million and $2.2 million for the three and nine months ended September 30, 2017, respectively.

Restricted Stock Units

The following table summarizes the restricted stock unit activity for the nine months ended September 30, 2018:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2018	731,975	$	22.16
Granted	307,896	30.33
Vested	(6,300)	20.38
Canceled	(11,601)	25.77
Non-vested outstanding at September 30, 2018	1,021,970	24.59

As of September 30, 2018, total unrecognized compensation cost related to unvested restricted stock units was approximately $21.2 million, which will be recognized over a weighted average period of 2.5 years.

The following table summarizes the components of our stock-based compensation expense for the three and nine months ended September 30, 2018 and 2017 (in thousands):


	Three Months Ended September 30,						Nine Months Ended September 30,
	2018		2017		2018		2017
Stock-based compensation expense related to stock options	$	5,232	$	1,440	$	7,559	$	8,261
Stock-based compensation expense related to restricted stock units	1,477		134		3,388		134
Stock-based compensation expense related to the issuance of common stock to directors	92		—		300		130
Stock-based compensation expense related to stock options modifications	—		—		—		2,394
Total stock-based compensation expense	$	6,801	$	1,574	$	11,247	$	10,919

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 condensed consolidated statements of operations for the three and nine months ended September 30, 2018 and 2017 (in thousands):


	Three Months Ended September 30,						Nine Months Ended September 30,
	2018		2017		2018		2017
Cost of revenue
Subscriptions, software and support	$	138	$	80	$	355	$	484
Professional services	222		142		645		1,126
Operating expenses
Sales and marketing	736		359		1,781		2,782
Research and development	373		256		1,106		2,458
General and administrative	5,332		737		7,360		4,069
Total stock-based compensation expense	$	6,801	$	1,574	$	11,247	$	10,919

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders’ EquityAs of September 30, 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 $0.0001 per share, of which 28,036,799 shares of Class A common stock and 35,551,517 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.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	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 and the Netherlands, under non-cancellable operating lease agreements which have various expiration dates through 2026 for our office space and various expiration dates through 2019 for our equipment. In April 2018, we entered into a new lease agreement for a new headquarters in Tysons, Virginia. The lease term commenced on October 1, 2018, for a period of 150 months. 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. In connection with entering into the lease agreement, we amended our sublease with College Entrance Examination Board, which will terminate the sublease agreement. Pursuant to the termination amendment, the sublease will terminate in two stages, with the termination of a majority of the premises taking place on May 31, 2019, rather than July 31, 2021 as originally contemplated by the sublease. 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 September 30, 2018 and December 31, 2017, deferred rent totaled $0.7 million and $2.0 million, respectively, and is included within other current liabilities and other long-term liabilities on the accompanying consolidated balance sheets. Total rent and lease expense was $1.9 million and $5.8 million for the three and nine months ended September 30, 2018, respectively. Total rent and lease expense was $1.7 million and $5.2 million for the three and nine months ended September 30, 2017, 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 September 30, 2018 and December 31, 2017, we had outstanding letters of credit totaling $10.4 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 4. 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

9 Months Ended

Sep. 30, 2018

Segment Reporting [Abstract]

Segment and Geographic Information

The following table summarizes revenue by geography for the three and nine months ended September 30, 2018 and 2017 (in thousands):


	Three Months Ended September 30,						Nine Months Ended September 30,
	2018		2017		2018		2017
Domestic	$	38,982	$	31,878	$	116,498	$	93,860
International	15,966		12,770		50,029		32,315
Total	$	54,948	$	44,648	$	166,527	$	126,175

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 three and nine months ended September 30, 2018 and 2017. Substantially all of our long-lived assets were held in the United States as of September 30, 2018 and December 31, 2017.

Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements and footnotes have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as contained in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (the “Codification” or “ASC”) for interim financial information. In the opinion of management, the interim financial information includes all adjustments of a normal recurring nature necessary for a fair presentation of the results of operations, financial position, changes in stockholders’ equity and cash flows. The results of operations for the current period are not necessarily indicative of the results for the full year or the results for any future periods. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2017, filed with the Securities and Exchange Commission (the “SEC”) on February 23, 2018.
Use of Estimates	Use of Estimates The preparation of our condensed consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and judgments that affect the amounts reported in these condensed 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 condensed 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 condensed consolidated financial statements include the accounts of Appian and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Revenue Recognition, Deferred Revenue, and Cost of Revenue	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 general 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. As a result, revenue from our perpetual software licenses during the three months ended September 30, 2018 was less than 1.0% of our total revenue. However, during the nine months ended September 30, 2018, we sold a $4.4 million perpetual software license to the U.S. Air Force. Therefore, revenue from our perpetual software licenses was 2.7% of our total revenue for the nine months ended September 30, 2018. Revenue from our perpetual software licenses was less than 1.0% of our total revenue for the three and nine months ended September 30, 2017. 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	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. Cash deposits may be in excess of insured limits. 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.
Accounts Receivable and Allowance for Doubtful Accounts	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. There was no change in the allowance for doubtful accounts from December 31, 2017 to September 30, 2018.
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 condensed consolidated statements of operations. Commission expense was $4.0 million and $10.2 million for the three and nine months ended September 30, 2018, respectively. Commission expense was $3.2 million and $8.5 million for the three and nine months ended September 30, 2017, respectively.
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 September 30, 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 CompensationWe 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 Options Pricing Model. 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 model 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.
Emerging Growth Company Status	Emerging Growth Company Status We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act (“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 SEC 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 are required to complete our tax accounting for the TCJA in the period when we have obtained, prepared, and analyzed the information to complete the income tax accounting. We have not completed our accounting for the tax effects of enactment of the TCJA; however, we have made reasonable estimates of the effects of the TCJA on our consolidated financial statements which are included as a component of income tax expense. In March 2018, the FASB issued Accounting Standards Update No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 ("ASU 2018-05"), which allowed SEC registrants to record provisional amounts in earnings for the year ended December 31, 2017 due to the complexities involved in accounting for the enactment of the TCJA. In accordance with SAB No. 118, we recognized the estimated income tax effects of the TCJA in the consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2017, filed with the SEC on February 23, 2018. See Note 5 for further information regarding the provisional amounts recorded as of December 31, 2017. 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 three and nine months ended September 30, 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 intend to avail ourselves of the JOBS Act extended transition period that permits us to defer adoption until January 1, 2019. The Topic 606 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 currently plan 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 may 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 since having a direct relationship with a contract is no longer required. 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 Topic 606 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. 2016-02, Leases (Topic 842) (“ASU 2016-02”), 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 2016-02 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 are currently in the process of evaluating the impact of adoption of this standard on our consolidated financial statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income ("ASU 2018-02"), which provides entities the option to reclassify to retained earnings tax effects related to items in accumulated other comprehensive income ("OCI") that the FASB refers to as having been stranded in accumulated OCI as a result of tax reform. ASU 2018-02 is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. We do not expect ASU 2018-02 to have a material impact on our consolidated financial statements.

Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following table presents the changes in our Level 3 instruments measured at fair value on a recurring basis during the nine months ended September 30, 2017 (in thousands):


	Nine Months Ended
	September 30, 2017
Balance as of January 1	$	850
Change in fair value of warrant liability	341
Reclassification of warrant liability to equity	(1,191)
Balance as of September 30	$	—

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 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 three and nine months ended September 30, 2018 and 2017:


	Three Months Ended September 30,			Nine Months Ended September 30,
	2018	2017	2018	2017
Risk-free interest rate	*	1.9% - 2.1%	*	1.9% - 2.2%
Expected term (in years)	*	6.5	*	6.5
Expected volatility	*	38.6%	*	38.6% - 40.6%
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 nine months ended September 30, 2018:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
January 1, 2018	7,010,887	$	6.36	6.6	$	176,122
Granted	—	—
Exercised	(1,297,979)	2.01			36,911
Canceled	(70,424)	9.34
Outstanding at September 30, 2018	5,642,484	7.32		6.6	145,456
Exercisable at September 30, 2018	3,905,924	6.37		6.1	104,395

Schedule of Restricted Stock Unit Activity

The following table summarizes the restricted stock unit activity for the nine months ended September 30, 2018:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2018	731,975	$	22.16
Granted	307,896	30.33
Vested	(6,300)	20.38
Canceled	(11,601)	25.77
Non-vested outstanding at September 30, 2018	1,021,970	24.59

Schedule of Components of Stock-based Compensation Expense

The following table summarizes the components of our stock-based compensation expense for the three and nine months ended September 30, 2018 and 2017 (in thousands):


	Three Months Ended September 30,						Nine Months Ended September 30,
	2018		2017		2018		2017
Stock-based compensation expense related to stock options	$	5,232	$	1,440	$	7,559	$	8,261
Stock-based compensation expense related to restricted stock units	1,477		134		3,388		134
Stock-based compensation expense related to the issuance of common stock to directors	92		—		300		130
Stock-based compensation expense related to stock options modifications	—		—		—		2,394
Total stock-based compensation expense	$	6,801	$	1,574	$	11,247	$	10,919

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


	Three Months Ended September 30,						Nine Months Ended September 30,
	2018		2017		2018		2017
Cost of revenue
Subscriptions, software and support	$	138	$	80	$	355	$	484
Professional services	222		142		645		1,126
Operating expenses
Sales and marketing	736		359		1,781		2,782
Research and development	373		256		1,106		2,458
General and administrative	5,332		737		7,360		4,069
Total stock-based compensation expense	$	6,801	$	1,574	$	11,247	$	10,919

Basic and Diluted Loss per Common Share (Tables)

9 Months Ended

Sep. 30, 2018

Earnings Per Share [Abstract]

Summary of Securities Excluded From Calculation of Weighted Average Common Shares

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:


	Three Months Ended September 30,			Nine Months Ended September 30,
	2018	2017	2018	2017
Stock options	5,642,484	7,383,928	5,642,484	7,383,928
Restricted stock units	1,021,970	42,925	1,021,970	42,925

Segment and Geographic Information (Tables)

9 Months Ended

Sep. 30, 2018

Segment Reporting [Abstract]

Summary of Revenue By Geography

The following table summarizes revenue by geography for the three and nine months ended September 30, 2018 and 2017 (in thousands):


	Three Months Ended September 30,						Nine Months Ended September 30,
	2018		2017		2018		2017
Domestic	$	38,982	$	31,878	$	116,498	$	93,860
International	15,966		12,770		50,029		32,315
Total	$	54,948	$	44,648	$	166,527	$	126,175

Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) agency	Sep. 30, 2017 USD ($)	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Number of shares issued in public offering (in shares) \| shares	2,000,000
Number of shares issued in public offering, by the Company (in shares) \| shares	1,675,000
Number of shares issued in public offering, by the existing shareholders (in shares) \| shares	325,000
Exercise price of shares sold in public offering (in usd per share) \| $ / shares	$ 35.15
Net proceeds from public offering	$ 57,800,000
Percentage of license revenue (less than)		1.00%	1.00%	2.70%	100.00%
Sale of perpetual software deal				$ 4,400,000
Change in allowance for doubtful accounts				0
Commission expense		$ 4,000,000.0	$ 3,200,000	$ 10,200,000	$ 8,500,000
Customer Concentration Risk \| Sales Revenue, Net \| Foreign Customers
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		29.10%	28.60%	30.00%	25.60%
Customer Concentration Risk \| Sales Revenue, Net \| Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		14.10%	14.20%	16.10%	15.40%
Customer Concentration Risk \| Sales Revenue, Net \| Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		7.20%	7.70%	8.70%	9.10%
Number of federal government agencies \| agency				3
Customer Concentration Risk \| Accounts Receivable \| Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage				3.70%		7.00%
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

Significant Accounting Policies Significant Accounting Policies - Summary of Changes in Level 3 Instruments Measured at Fair Value On Recurring Basis (Detail) - Fair Value, Measurements, Recurring - Fair Value, Inputs, Level 3 $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 850
Change in fair value of warrant liability	341
Reclassification of warrant liability to equity	(1,191)
Ending balance	$ 0

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued contract labor costs	$ 2,307	$ 3,424
Accrued audit and tax professional fees	629	248
Accrued hosting costs	522	466
Accrued third party license fees	753	235
Accrued reimbursable employee expenses	405	286
Accrued marketing and tradeshow expenses	319	128
Other accrued expenses	1,663	1,680
Total	$ 6,598	$ 6,467

Debt - Additional Information (Detail) - USD ($)	1 Months Ended	9 Months Ended
Debt - Additional Information (Detail) - USD ($)	Nov. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Apr. 30, 2017
Line of Credit Facility [Line Items]
Loss on extinguishment of debt		$ 0	$ 384,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility	$ 20,000,000.0	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 credit facility fee	0.15%
Quick ratio	135.00%
Minimum \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Interest rate margin	2.00%
Minimum \| Prime Rate
Line of Credit Facility [Line Items]
Interest rate margin	1.00%
Maximum
Line of Credit Facility [Line Items]
Unused credit facility fee	0.25%
Maximum \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Interest rate margin	2.50%
Maximum \| Prime Rate
Line of Credit Facility [Line Items]
Interest rate margin	1.50%

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Taxes [Line Items]
Effective tax rate	0.20%	(3.10%)	(0.60%)	(2.10%)
Net unrecognized tax benefits which would impact effective tax rate if recognized	$ 0.7		$ 0.7
Earliest Tax Year
Income Taxes [Line Items]
Open tax year			2014
Latest Tax Year
Income Taxes [Line Items]
Open tax year			2017
Minimum \| Subsidiaries
Income Taxes [Line Items]
Effective tax rate			0.00%
Maximum \| Subsidiaries
Income Taxes [Line Items]
Effective tax rate			33.00%

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended		9 Months Ended
	Apr. 25, 2017	May 31, 2017	Jul. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grants				0		0
Service period for option exercise						5 years
Stock-based compensation expense				$ 6,801	$ 1,574	$ 11,247	$ 10,919
Granted (in usd per share)							$ 5.04
Vested						10,200	$ 5,300
Compensation cost related to nonvested stock options not yet recognized				3,200		$ 3,200
Unrecognized compensation cost related to nonvested stock option recognized over weighted average period, in years						2 years 2 months 12 days
Stock options to purchase common stock (in shares)	216,160
Granted						0
Exercise price of stock options granted (in usd per share)						$ 0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested restricted stock units				21,200		$ 21,200
Weighted average remaining vesting period						2 years 6 months
Cumulative Stock-based Compensation Expense Related to Stock Options Recorded upon Effectiveness of Our IPO \| 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			0	0	$ 0	2,394
CEO Grant Of 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 4,700	$ 500	$ 5,600	$ 2,200
Number of shares vested and exercisable (in shares)				1,828,080		1,828,080
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available to be issued				5,540,439		5,540,439
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		6,607,686		6,607,686
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
Chief Executive Officer \| 2007 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			1,828,080
Exercise price of stock options granted (in usd per share)			$ 9.46

Stock-Based Compensation - Summary of Estimate the Fair Value of Stock Options Granted (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Share-based Goods and Nonemployee Services Transaction [Line Items]
Expected term (in years)	6 years 6 months	6 years 6 months
Expected volatility	38.60%
Expected dividend yield	0.00%	0.00%
Minimum
Share-based Goods and Nonemployee Services Transaction [Line Items]
Risk-free interest rate	1.90%	1.90%
Expected volatility		38.60%
Maximum
Share-based Goods and Nonemployee Services Transaction [Line Items]
Risk-free interest rate	2.10%	2.20%
Expected volatility		40.60%

Stock-Based Compensation - Summary of the Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Number of Shares
January 1, 2018	7,010,887
Granted	0
Exercised	(1,297,979)
Canceled	(70,424)
Outstanding at September 30, 2018	5,642,484	7,010,887
Exercisable at September 30, 2018	3,905,924
Weighted Average Exercise Price
January 1, 2018	$ 6.36
Granted	0
Exercised	2.01
Canceled	9.34
Outstanding at September 30, 2018	7.32	$ 6.36
Exercisable at September 30, 2018	$ 6.37
Weighted Average Remaining Contractual Term (Years)
January 1, 2018	6 years 7 months 6 days	6 years 7 months 6 days
Outstanding at September 30, 2018	6 years 7 months 6 days	6 years 7 months 6 days
Exercisable at September 30, 2018	6 years 1 month 6 days
Aggregate Intrinsic Value (in thousands)
January 1, 2018	$ 176,122
Exercised	36,911
Outstanding at September 30, 2018	145,456	$ 176,122
Exercisable at September 30, 2018	$ 104,395

Stock-Based Compensation - Schedule of Restricted Stock Unit Activity (Detail)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Number of Shares
Vested	(6,300)
Restricted Stock Units
Number of Shares
Non-vested outstanding at January 1, 2018	731,975
Granted	307,896
Vested	(6,300)
Canceled	(11,601)
Non-vested outstanding at September 30, 2018	1,021,970
Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2018 \| $ / shares	$ 22.16
Granted \| $ / shares	30.33
Vested \| $ / shares	20.38
Canceled \| $ / shares	25.77
Non-vested outstanding at September 30, 2018 \| $ / shares	$ 24.59

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 25, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense		$ 6,801	$ 1,574	$ 11,247	$ 10,919
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense		5,232	1,440	7,559	8,261
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense		1,477	134	3,388	134
Issuance Of Common Stock To Directors
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense		92	0	300	130
Stock Option Modifications
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,400	$ 0	$ 0	$ 0	$ 2,394

Stock-Based Compensation - Schedule of Stock-based Compensation Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 6,801	$ 1,574	$ 11,247	$ 10,919
Subscriptions, Software, And Support
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	138	80	355	484
Professional Services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	222	142	645	1,126
Selling and Marketing Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	736	359	1,781	2,782
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	373	256	1,106	2,458
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 5,332	$ 737	$ 7,360	$ 4,069

Stockholders' Equity (Detail)	9 Months Ended
Stockholders' Equity (Detail)	Sep. 30, 2018 vote_per_share $ / shares shares	Dec. 31, 2017 $ / shares shares
Class of Stock [Line Items]
Common stock, par value \| $ / shares	$ 0.0001
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized	500,000,000	500,000,000
Common stock, par value \| $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued	28,036,799	13,030,081
Common stock, shares outstanding	28,036,799	13,030,081
Number of votes entitled to stockholders per share \| vote_per_share	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]
Common stock, shares authorized	100,000,000	100,000,000
Common stock, par value \| $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued	35,551,517	47,569,796
Common stock, shares outstanding	35,551,517	47,569,796
Number of votes entitled to stockholders per share \| vote_per_share	10

Basic and Diluted Loss per Common Share - Summary of Securities Excluded From Calculation of Weighted Average Common Shares Outstanding (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	5,642,484	7,383,928	5,642,484	7,383,928
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	1,021,970	42,925	1,021,970	42,925

Commitments and Contingencies -Narrative (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Lease term (in months)	150 months
Total payments committed under operating lease	$ 87.2
Deferred rent, noncurrent		$ 0.7		$ 0.7		$ 2.0
Total rent and lease expense		1.9	$ 1.7	5.8	$ 5.2
Payment of royalty fees				0.3
Outstanding letters of credit		$ 10.4		$ 10.4		$ 1.1
Letter of Credit
Debt Instrument [Line Items]
Letter of credit entered into in connection with lease	$ 9.4

Segment and Geographic Information - Summary of Revenues By Geography (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 54,948	$ 44,648	$ 166,527	$ 126,175
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	38,982	31,878	116,498	93,860
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 15,966	$ 12,770	$ 50,029	$ 32,315

Segment and Geographic Information - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Sales Revenue, Net \| Geographic Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%	10.00%	10.00%	10.00%