Cover Page - shares	6 Months Ended
Cover Page - shares	Jun. 30, 2019	Aug. 05, 2019
Document and Entity Information [Line Items]
Document Type	10-Q
Entity File Number	001-38098
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity Registrant Name	APPIAN CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	54-1956084
Entity Address, Address Line One	7950 Jones Branch Drive
Entity Address, City or Town	Tysons
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	22102
Local Phone Number	442-8844
City Area Code	(703)
Title of 12(b) Security	Class A Common Stock
Trading Symbol	APPN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Central Index Key	0001441683
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Class A Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		31,509,538
Class B Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		33,374,676
Former Address
Document and Entity Information [Line Items]
Entity Address, Address Line One	11955 Democracy Drive, Suite 1700
Entity Address, City or Town	Reston
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	20190

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 81,101	$ 94,930
Accounts receivable, net of allowance of $600 as of June 30, 2019 and December 31, 2018	70,381	79,383
Allowance for doubtful accounts	600	600
Deferred commissions, current	17,492	14,020
Prepaid expenses and other current assets	7,707	21,293
Total current assets	176,681	209,626
Property and equipment, net	36,823	7,539
Deferred commissions, net of current portion	13,897	15,088
Deferred tax assets	445	326
Other assets	585	601
Total assets	228,431	233,180
Current liabilities
Accounts payable	10,173	9,249
Accrued expenses	12,075	7,464
Accrued compensation and related benefits	10,563	13,796
Deferred revenue, current	97,556	95,523
Capital leases, current	1,169	0
Other current liabilities	1,852	2,369
Total current liabilities	133,388	128,401
Deferred tax liabilities	20	42
Deferred revenue, net of current portion	14,597	16,145
Deferred rent, net of current portion	20,150	15,400
Capital leases, net of current portion	2,504	0
Total liabilities	170,659	159,988
Stockholders’ equity
Additional paid-in capital	230,185	218,284
Accumulated other comprehensive income	152	542
Accumulated deficit	(172,571)	(145,640)
Total stockholders’ equity	57,772	73,192
Total liabilities and stockholders’ equity	228,431	233,180
Class A Common Stock
Stockholders’ equity
Common stock	$ 3	$ 3
Common stock, par value (in usd per share)	$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	31,462,892	29,626,054
Common stock, shares outstanding (in shares)	31,462,892	29,626,054
Class B Common Stock
Stockholders’ equity
Common stock	$ 3	$ 3
Common stock, par value (in usd per share)	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	33,374,676	34,290,383
Common stock, shares outstanding (in shares)	33,374,676	34,290,383

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Total revenue	$ 66,911	$ 59,883	$ 126,490	$ 111,579
Cost of revenue:
Total cost of revenue	23,051	21,574	47,117	42,623
Gross profit	43,860	38,309	79,373	68,956
Operating expenses:
Sales and marketing	31,148	27,384	61,093	50,348
Research and development	12,765	10,785	26,721	20,655
General and administrative	9,261	8,425	18,277	16,485
Total operating expenses	53,174	46,594	106,091	87,488
Operating loss	(9,314)	(8,285)	(26,718)	(18,532)
Other (income) expense:
Other (income) expense, net	(256)	2,593	(316)	1,675
Interest expense	69	54	140	67
Total other (income) expense	(187)	2,647	(176)	1,742
Loss before income taxes	(9,127)	(10,932)	(26,542)	(20,274)
Income tax expense	267	35	389	246
Net loss	$ (9,394)	$ (10,967)	$ (26,931)	$ (20,520)
Net loss per share attributable to common stockholders:
Basic and diluted (in dollar per share)	$ (0.15)	$ (0.18)	$ (0.42)	$ (0.34)
Weighted average common shares outstanding:
Basic and diluted (in shares)	64,753,044	61,401,466	64,531,089	61,127,516
Subscriptions, Software, And Support
Revenue:
Total revenue	$ 39,259	$ 33,047	$ 74,168	$ 59,999
Cost of revenue:
Total cost of revenue	4,036	2,824	7,621	5,452
Professional Services
Revenue:
Total revenue	27,652	26,836	52,322	51,580
Cost of revenue:
Total cost of revenue	$ 19,015	$ 18,750	$ 39,496	$ 37,171

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (9,394)	$ (10,967)	$ (26,931)	$ (20,520)
Comprehensive loss, net of income taxes:
Foreign currency translation adjustment	(730)	1,103	(390)	537
Total other comprehensive loss, net of income taxes	$ (10,124)	$ (9,864)	$ (27,321)	$ (19,983)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	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	(20,520)				(20,520)
Issuance of common stock to directors (in shares)		6,605
Exercise of stock options (in shares)		1,006,398
Exercise of stock options	2,072		2,072
Stock-based compensation expense	4,446		4,446
Other comprehensive income (loss)	537			537
Ending balance (in shares) at Jun. 30, 2018		61,612,880
Ending balance at Jun. 30, 2018	32,059	$ 6	147,786	976	(116,709)
Beginning balance (in shares) at Dec. 31, 2018		63,916,437
Beginning balance at Dec. 31, 2018	73,192	$ 6	218,284	542	(145,640)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (26,931)				(26,931)
Issuance of common stock to directors (in shares)		6,145
Vesting of restricted stock units (in shares)		284,690
Exercise of stock options (in shares)	630,296	630,296
Exercise of stock options	$ 1,987		1,987
Stock-based compensation expense	9,914		9,914
Other comprehensive income (loss)	(390)			(390)
Ending balance (in shares) at Jun. 30, 2019		64,837,568
Ending balance at Jun. 30, 2019	$ 57,772	$ 6	$ 230,185	$ 152	$ (172,571)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (26,931)	$ (20,520)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	1,933	951
Loss on disposal of equipment	145	0
Bad debt expense	97	0
Deferred income taxes	(47)	77
Stock-based compensation	9,914	4,446
Changes in assets and liabilities:
Accounts receivable	8,861	(9,095)
Prepaid expenses and other assets	13,453	(311)
Deferred commissions	(2,281)	(3,062)
Accounts payable and accrued expenses	5,458	3,480
Accrued compensation and related benefits	(3,181)	1,995
Other current liabilities	(269)	951
Deferred revenue	189	(1,368)
Deferred rent, non-current	4,584	(1,160)
Net cash provided by (used in) operating activities	11,925	(23,616)
Cash flows from investing activities:
Purchases of property and equipment	(27,689)	(1,593)
Net cash used in investing activities	(27,689)	(1,593)
Cash flows from financing activities:
Proceeds from exercise of common stock options	1,987	2,072
Net cash provided by financing activities	1,987	2,072
Effect of foreign exchange rate changes on cash and cash equivalents	(52)	(258)
Net decrease in cash and cash equivalents	(13,829)	(23,395)
Cash and cash equivalents, beginning of period	94,930	73,758
Cash and cash equivalents, end of period	81,101	50,363
Supplemental disclosure of cash flow information:
Cash paid for interest	170	21
Cash paid for income taxes	116	175
Capital lease obligations to acquire new office furniture and fixtures	$ 3,673	$ 0

Significant Accounting Policies

6 Months Ended

Jun. 30, 2019

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 (“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, 2018, filed with the Securities and Exchange Commission (the “SEC”) on February 21, 2019.

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 and stock-based compensation.

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

We generate revenue primarily through sales of subscriptions to our platform, as well as professional services. 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.

We generally charge subscription fees on a per-user basis or, alternatively, 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 three 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 three years in length, with more recent contracts trending towards one year 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.

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 and term license subscriptions 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.

Deferred Revenue

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

Cost of Revenue

Cost of Subscriptions, Software and Support Revenue

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

Cost of Professional Services Revenue

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

Concentration of Credit Risk

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

With regard to our customers, credit evaluation and account monitoring procedures are used to minimize the risk of loss. We believe that no additional credit risk beyond amounts provided for collection loss are inherent in accounts receivable. Revenue generated from government agencies represented 17.3% and 17.6% of our revenue for the three and six months ended June 30, 2019, respectively, of which the top three federal government agencies generated 6.3% and 7.0% of our revenue for the three and six months ended June 30, 2019, respectively. Additionally, 30.8% and 30.3% of our revenue during the three and six months ended June 30, 2019, respectively, was generated from foreign customers. Revenue generated from government agencies represented 20.1% and 16.5% of our revenue for the three and six months ended June 30, 2018, respectively, of which the top three federal government agencies generated 13.5% and 9.8% of our revenue for the three and six months ended June 30, 2018, respectively. Additionally, 28.1% and 29.6% of our revenue during the three and six months ended June 30, 2018, respectively, was generated from foreign customers.

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, 2018 to June 30, 2019.

Non-Trade Receivables

We record non-trade receivables to reflect amounts due for activities other than sales of subscriptions to our platform and professional services. Our non-trade receivables relate entirely to a receivable from our tenant improvement allowance. We received the entire tenant improvement allowance as of June 30, 2019, and therefore, there was no receivable balance remaining as of such date. The tenant improvement allowance receivable was $14.4 million as of December 31, 2018 and is classified within prepaid expenses and other current assets in the accompanying condensed consolidated balance sheets. We recognized our initial tenant improvement allowance receivable of $15.8 million related to our new headquarters once we took initial possession of the space in October 2018. We recognized additional tenant improvement allowance receivable of $2.6 million when we took possession of adjacent office space in February 2019.

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 $4.7 million and $9.1 million for the three and six months ended June 30, 2019, respectively. Commission expense was $3.5 million and $6.2 million for the three and six months ended June 30, 2018, respectively.

Property and Equipment

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


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

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 June 30, 2019 and December 31, 2018 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 instruments measured at fair value during the three and six months ended June 30, 2019 and June 30, 2018.

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

Emerging Growth Company Status

We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act (the “JOBS Act”). We will remain an emerging growth company until December 31, 2019. After that date, we will no longer be an "emerging growth company" but will then be a "large accelerated filer," because over $700 million of our outstanding equity securities was held by non-affiliates as of June 30, 2019. 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

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. The adoption of ASU 2016-15 did not have an impact on our condensed consolidated financial statements for the three and six months ended June 30, 2019.

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. The adoption of ASU 2018-02 did not have an impact on our condensed consolidated financial statements for the three and six months ended June 30, 2019.

Not Yet Adopted

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASC 606”), which provides new guidance for revenue recognition. ASC 606 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. ASC 606 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 ASC 606. 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 ASC 606. In addition, in May 2016, the FASB issued ASU No. 2016-12, Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), which clarifies the guidance on assessing collectibility, presentation of sales taxes, noncash consideration and completed contracts and contract modifications at transition. For public entities, the new standard is effective for annual periods and interim periods within those annual periods, beginning after December 15, 2017. For all other entities, the new standard is effective for annual periods beginning after December 15, 2018, and interim periods within those annual periods beginning after December 15, 2019. We have elected to avail ourselves of the JOBS Act extended transition period that permits us to defer adoption until January 1, 2019. In accordance with guidance, the new standard will be adopted in our Annual Report on Form 10-K for the fiscal year ending December 31, 2019 but will not be adopted in our Quarterly Reports on Form 10-Q to be filed during 2019.

The ASC 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 are going to adopt the new standard using the modified retrospective method.

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

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

We are still in the process of quantifying the effects of the adoption of ASC 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 was further clarified by ASU No. 2018-10, Codification Improvements to Topic 842, Leases, and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, both issued in July 2018. ASU 2016-02 requires companies to recognize on the balance sheet the assets and liabilities for the rights and obligations created by lease assets. The new standard also requires additional disclosure of qualitative and quantitative information about the amounts recorded in the financial statements related to lease agreements. Because we will lose "emerging growth company" status effective December 31, 2019, the new standard will be adopted in our Annual Report on Form 10-K for the year ending December 31, 2019. ASU 2016-02 requires a transition adoption election of either (1) a modified retrospective approach with periods prior to the adoption date being restated or (2) a prospective adoption approach with a cumulative-effect adjustment recognized to the opening balance of retained earnings on the adoption date with prior periods not restated. We are currently evaluating the impact the adoption of ASU 2016-02 will have on our condensed consolidated financial statements. We plan to adopt this standard using the prospective adoption approach and electing the practical expedients allowed under the standard. Although we are still evaluating the impact of the adoption of the standard on our condensed consolidated financial statements, we expect there will be a material increase to assets and liabilities related to the recognition of new right-of-use assets and lease liabilities on our balance sheet for leases currently classified as operating leases.

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

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018-13"), which eliminates, modifies and adds disclosure requirements for fair value measurements. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early application will be permitted. We do not expect ASU 2018-13 to have a material impact on our consolidated financial statements.

Stock-Based Compensation

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [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 initial public offering. 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 June 30, 2019, there were 7,084,603 shares of Class A common stock reserved for issuance under the 2017 Plan, of which 4,913,160 were available to be issued.

The 2007 Plan provided for the grant of stock options to employees, directors, and officers. Stock options under the 2007 Plan are exercisable into shares of Class B common stock and generally expire ten years from the date of grant. Under the 2007 Plan, the exercise price of each award was established by the board of directors, but could not be less than the fair market value of a share of our common stock on the grant date. Stock options generally vest upon the satisfaction of both a service condition and a performance condition. The service condition is satisfied at various rates as determined by us, typically on an annual basis over five years. The performance condition required the occurrence of a qualifying event, defined as a change of control transaction or upon the completion of an initial public offering. The performance condition was satisfied upon the effectiveness of our initial public offering in May 2017.

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

In May 2019, our board of directors granted a stock option to purchase 700,000 shares of our Class A common stock to our Chief Executive Officer (the "2019 CEO Grant") under the 2017 Plan with an exercise price of $33.98 per share. The 2019 CEO Grant is eligible to vest based on the achievement of a stock price appreciation target of our Class A common stock. Specifically, the 2019 CEO Grant will vest when shares of our Class A common stock closes at or above $84.63 per share for a period equal to or greater than 90 calendar days or upon the occurrence of a change in control in which the value of our Class A common stock is equal to or greater than $84.63 per share within five years of the grant date. The fair value of the 2019 CEO Grant was determined using a Monte Carlo simulation. The fair value of the award at the grant date was $9.5 million and will be amortized over the derived service period of 2.6 years.

The following table summarizes the assumptions used to estimate the fair value of stock options granted during the three and six months ended June 30, 2019 and 2018:


	Three Months Ended June 30,			Six Months Ended June 30,
	2019	2018	2019	2018
Risk-free interest rate	2.1%	*	2.1%	*
Expected term (in years)	2.6	*	2.6	*
Expected volatility	55.0%	*	55.0%	*
Expected dividend yield	—%	*	—%	*

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

Stock Options

The following table summarizes the stock option activity for the six months ended June 30, 2019:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
January 1, 2019	5,021,068	$	7.30	6.4	$	97,440
Granted	700,000	33.98
Exercised	(630,296)	3.15			18,852
Canceled	(44,140)	10.45
Outstanding at June 30, 2019	5,046,632	11.49		6.2	124,021
Exercisable at June 30, 2019	3,207,972	7.12		6.0	92,872

The weighted average grant-date fair value of stock options granted during the six months ended June 30, 2019 was $13.57 per share. No stock options were granted during the six months ended June 30, 2018. The total fair value of stock options that vested during the six months ended June 30, 2019 and 2018 was $1.5 million and $1.6 million, respectively. As of June 30, 2019, the total compensation cost related to unvested stock options not yet recognized was $10.9 million, which will be recognized over a weighted average period of 2.4 years.

Restricted Stock Units

The following table summarizes the restricted stock unit activity for the six months ended June 30, 2019:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2019	1,175,049	$	26.04
Granted	126,065	35.02
Vested	(284,690)	30.03
Canceled	(20,375)	28.70
Non-vested outstanding at June 30, 2019	996,049	25.99

As of June 30, 2019, total unrecognized compensation cost related to unvested restricted stock units was approximately $20.6 million, which will be recognized over a weighted average period of 2.3 years.

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

The following table summarizes the components of our stock-based compensation expense for the three and six months ended June 30, 2019 and 2018 (in thousands):


	Three Months Ended June 30,						Six Months Ended June 30,
	2019		2018		2019		2018
Stock-based compensation expense related to restricted stock units	$	1,902	$	1,017	$	8,671	$	1,911
Stock-based compensation expense related to stock options	695		1,073		1,059		2,327
Stock-based compensation expense related to the issuance of common stock to directors	92		116		184		208
Total stock-based compensation expense	$	2,689	$	2,206	$	9,914	$	4,446

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 six months ended June 30, 2019 and 2018 (in thousands):


	Three Months Ended June 30,						Six Months Ended June 30,
	2019		2018		2019		2018
Cost of revenue
Subscriptions, software and support	$	161	$	107	$	315	$	217
Professional services	244		203		2,218		423
Operating expenses
Sales and marketing	814		538		3,195		1,045
Research and development	435		342		2,550		733
General and administrative	1,035		1,016		1,636		2,028
Total stock-based compensation expense	$	2,689	$	2,206	$	9,914	$	4,446

Commitments and Contingencies

6 Months Ended

Jun. 30, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

We lease office space and equipment under non-cancellable operating lease agreements which have various expiration dates through 2031 for our office space and various expiration dates through 2020 for our equipment.

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

The lease for the new headquarters contains a tenant improvement allowance of up to $18.4 million from the landlord. The tenant improvement allowance is accounted for as a lease incentive obligation and is amortized as a reduction to rent expense over the lease term. We recorded a lease incentive obligation when we took initial possession of the first phase of the new headquarters. We took initial possession of the second phase in February 2019 and recorded an additional lease incentive obligation. As of June 30, 2019, $1.4 million was included in other current liabilities and $16.0 million was included in deferred rent, net of current portion on the accompanying consolidated balance sheets. As of December 31, 2018, $1.2 million was included in other current liabilities and $14.4 million was included in deferred rent, net of current portion on the accompanying consolidated balance sheets.

Capital Leases

We lease certain office furniture and fixtures under non-cancellable capital lease agreements which have expiration dates in 2022. As of June 30, 2019, office furniture and fixtures acquired under capital lease agreements totaled $3.7 million. There were no assets acquired under capital lease agreements as of December 31, 2018.

A summary of our future minimum payments under non-cancellable operating and capital lease agreements by year as of June 30, 2019 is as follows (in thousands):


	Operating Leases		Capital Leases
Remainder of 2019	$	2,111	$	663
2020	3,375		1,325
2021	6,790		1,325
2022	6,938		663
2023	6,987		—
Thereafter	65,148		—
Total minimum lease payments	91,349		3,976
Less: amounts representing interest	—		(302)
Present value of lease obligations	$	91,349	$	3,674

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 June 30, 2019 and December 31, 2018, deferred rent totaled $21.5 million and $17.4 million, respectively, and is included within other current liabilities and deferred rent, net of current portion on the accompanying condensed consolidated balance sheets. In addition to rental payments, certain leases require additional payments for real estate taxes, common area maintenance and insurance, which are expensed when incurred and not included in future minimum payments.

Total rent and lease expense was $2.4 million and $5.5 million for the three and six months ended June 30, 2019, respectively. Total rent and lease expense was $1.8 million and $3.8 million for the three and six months ended June 30, 2018, 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 each of June 30, 2019 and December 31, 2018, we had outstanding letters of credit totaling $10.5 million in connection with securing our leased office space. All letters of credit are secured by our borrowing arrangement as described in Note 5.

Legal

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

Significant Accounting Policies (Policies)	6 Months Ended
Significant Accounting Policies (Policies)	Jun. 30, 2019
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 (“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, 2018, filed with the Securities and Exchange Commission (the “SEC”) on February 21, 2019.
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 and stock-based compensation.
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. 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. We generally charge subscription fees on a per-user basis or, alternatively, 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 three 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 three years in length, with more recent contracts trending towards one year 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. 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 and term license subscriptions 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. 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. Deposits held with banks may exceed the amount of insurance provided on such deposits. We believe that the financial institutions that hold our cash deposits are financially sound and, accordingly, minimal credit risk exists with respect to these balances. With regard to our customers, credit evaluation and account monitoring procedures are used to minimize the risk of loss. We believe that no additional credit risk beyond amounts provided for collection loss are inherent in accounts receivable.
Accounts Receivable and Allowance for Doubtful Accounts and Non-Trade Receivables	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, 2018 to June 30, 2019. Non-Trade Receivables We record non-trade receivables to reflect amounts due for activities other than sales of subscriptions to our platform and professional services. Our non-trade receivables relate entirely to a receivable from our tenant improvement allowance. We received the entire tenant improvement allowance as of June 30, 2019, and therefore, there was no receivable balance remaining as of such date. The tenant improvement allowance receivable was $14.4 million as of December 31, 2018 and is classified within prepaid expenses and other current assets in the accompanying condensed consolidated balance sheets. We recognized our initial tenant improvement allowance receivable of $15.8 million related to our new headquarters once we took initial possession of the space in October 2018. We recognized additional tenant improvement allowance receivable of $2.6 million when we took possession of adjacent office space in February 2019.
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.
Property and Equipment	Property and EquipmentProperty and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Significant additions or improvements extending the useful life of an asset are capitalized, while repairs and maintenance costs which do not significantly improve the related assets or extend their useful lives are charged to expense as incurred.
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 June 30, 2019 and December 31, 2018 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 containing only a service condition using the Black-Scholes Option Pricing Model. The fair value of restricted stock units is based on the closing market price of our common stock on the Nasdaq Global Market on the date of grant. For service-based awards, stock-based compensation expense is recognized on a straight-line basis over the requisite service period. For performance-based awards, stock-based compensation expense is recognized using the accelerated attribution method, based on the probability of satisfying the performance condition. For awards that contain market conditions, compensation expense is measured using a Monte Carlo simulation and recognized using the accelerated attribution method over the derived service period based on the expected market performance as of the grant date. For restricted stock units, stock-based compensation expense is recognized on a straight-line basis over the requisite service period. We account for forfeitures as they occur, rather than estimating expected forfeitures.
Emerging Growth Company Status	Emerging Growth Company StatusWe are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act (the “JOBS Act”). We will remain an emerging growth company until December 31, 2019. After that date, we will no longer be an "emerging growth company" but will then be a "large accelerated filer," because over $700 million of our outstanding equity securities was held by non-affiliates as of June 30, 2019. 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 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. The adoption of ASU 2016-15 did not have an impact on our condensed consolidated financial statements for the three and six months ended June 30, 2019. 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. The adoption of ASU 2018-02 did not have an impact on our condensed consolidated financial statements for the three and six months ended June 30, 2019. Not Yet Adopted In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASC 606”), which provides new guidance for revenue recognition. ASC 606 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. ASC 606 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 ASC 606. 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 ASC 606. In addition, in May 2016, the FASB issued ASU No. 2016-12, Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), which clarifies the guidance on assessing collectibility, presentation of sales taxes, noncash consideration and completed contracts and contract modifications at transition. For public entities, the new standard is effective for annual periods and interim periods within those annual periods, beginning after December 15, 2017. For all other entities, the new standard is effective for annual periods beginning after December 15, 2018, and interim periods within those annual periods beginning after December 15, 2019. We have elected to avail ourselves of the JOBS Act extended transition period that permits us to defer adoption until January 1, 2019. In accordance with guidance, the new standard will be adopted in our Annual Report on Form 10-K for the fiscal year ending December 31, 2019 but will not be adopted in our Quarterly Reports on Form 10-Q to be filed during 2019. The ASC 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 are going to adopt the new standard using the modified retrospective method. We do not expect the new standard to have a material impact on the timing of revenue recognition related to our cloud-based subscriptions and standalone professional services. However, we expect the new standard to have a significant impact on the timing of revenue recognition related to our on-premise term license contracts. Under current industry-specific software revenue recognition guidance, we have historically concluded that we did not have VSOE of fair value of the undelivered services related to on-premise term license contracts, and accordingly, have recognized on-premise term license contracts and related services ratably over the contract term. Under this new standard, the requirement to have VSOE for undelivered services is eliminated. Therefore, we will be required to recognize a portion of revenue from the on-premise term license contracts upon delivery of the software. In addition, we expect the new standard to impact our accounting for contract acquisition costs, both with respect to the amounts that will be capitalized as well as the period of amortization. Currently, we defer the direct and incremental commission costs to obtain a contract with a customer and amortize those costs over the term of the related customer contract consistent with the related revenue. Under the new standard, we will defer the incremental costs to obtain a contract with a customer. Therefore, the new standard will result in additional costs being capitalized, including fringe benefits. Under the new standard, initial incremental costs to obtain a contract will be amortized over the customer's estimated economic life of five years, which was calculated based on both qualitative and quantitative factors, such as product life cycles, contractual terms and customer attrition. Incremental contract costs paid relating to contract renewals will be deferred and amortized on a straight-line basis over the related renewal period. As a result, we expect the deferred commissions asset to increase and the related amortization expense in each reporting period to decrease under the new standard. We are still in the process of quantifying the effects of the adoption of ASC 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 was further clarified by ASU No. 2018-10, Codification Improvements to Topic 842, Leases, and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, both issued in July 2018. ASU 2016-02 requires companies to recognize on the balance sheet the assets and liabilities for the rights and obligations created by lease assets. The new standard also requires additional disclosure of qualitative and quantitative information about the amounts recorded in the financial statements related to lease agreements. Because we will lose "emerging growth company" status effective December 31, 2019, the new standard will be adopted in our Annual Report on Form 10-K for the year ending December 31, 2019. ASU 2016-02 requires a transition adoption election of either (1) a modified retrospective approach with periods prior to the adoption date being restated or (2) a prospective adoption approach with a cumulative-effect adjustment recognized to the opening balance of retained earnings on the adoption date with prior periods not restated. We are currently evaluating the impact the adoption of ASU 2016-02 will have on our condensed consolidated financial statements. We plan to adopt this standard using the prospective adoption approach and electing the practical expedients allowed under the standard. Although we are still evaluating the impact of the adoption of the standard on our condensed consolidated financial statements, we expect there will be a material increase to assets and liabilities related to the recognition of new right-of-use assets and lease liabilities on our balance sheet for leases currently classified as operating leases. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326) ("ASU 2016-13"), which requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. This replaces the existing incurred loss model and is applicable to the measurement of credit losses on financial assets measured at amortized cost. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early application will be permitted for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We are currently evaluating the impact that the standard will have on our consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018-13"), which eliminates, modifies and adds disclosure requirements for fair value measurements. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early application will be permitted. We do not expect ASU 2018-13 to have a material impact on our consolidated financial statements.

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [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 six months ended June 30, 2019 and 2018:


	Three Months Ended June 30,			Six Months Ended June 30,
	2019	2018	2019	2018
Risk-free interest rate	2.1%	*	2.1%	*
Expected term (in years)	2.6	*	2.6	*
Expected volatility	55.0%	*	55.0%	*
Expected dividend yield	—%	*	—%	*

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

Summary of the Stock Option Activity

The following table summarizes the stock option activity for the six months ended June 30, 2019:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
January 1, 2019	5,021,068	$	7.30	6.4	$	97,440
Granted	700,000	33.98
Exercised	(630,296)	3.15			18,852
Canceled	(44,140)	10.45
Outstanding at June 30, 2019	5,046,632	11.49		6.2	124,021
Exercisable at June 30, 2019	3,207,972	7.12		6.0	92,872

Schedule of Restricted Stock Unit Activity

The following table summarizes the restricted stock unit activity for the six months ended June 30, 2019:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2019	1,175,049	$	26.04
Granted	126,065	35.02
Vested	(284,690)	30.03
Canceled	(20,375)	28.70
Non-vested outstanding at June 30, 2019	996,049	25.99

Schedule of Components of Stock-based Compensation Expense

The following table summarizes the components of our stock-based compensation expense for the three and six months ended June 30, 2019 and 2018 (in thousands):


	Three Months Ended June 30,						Six Months Ended June 30,
	2019		2018		2019		2018
Stock-based compensation expense related to restricted stock units	$	1,902	$	1,017	$	8,671	$	1,911
Stock-based compensation expense related to stock options	695		1,073		1,059		2,327
Stock-based compensation expense related to the issuance of common stock to directors	92		116		184		208
Total stock-based compensation expense	$	2,689	$	2,206	$	9,914	$	4,446

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


	Three Months Ended June 30,						Six Months Ended June 30,
	2019		2018		2019		2018
Cost of revenue
Subscriptions, software and support	$	161	$	107	$	315	$	217
Professional services	244		203		2,218		423
Operating expenses
Sales and marketing	814		538		3,195		1,045
Research and development	435		342		2,550		733
General and administrative	1,035		1,016		1,636		2,028
Total stock-based compensation expense	$	2,689	$	2,206	$	9,914	$	4,446

Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($) agency	Dec. 31, 2018 USD ($)	Feb. 28, 2019 USD ($)	Oct. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Change in allowance for doubtful accounts			$ 0		$ 0
Tenant improvement allowance receivable					$ 14,400,000		$ 15,800,000
Additional tenant improvement receivable						$ 2,600,000
Commission expense	$ 4,700,000	$ 3,500,000	$ 9,100,000	$ 6,200,000
Customer Concentration Risk \| Sales Revenue, Net \| Foreign Customers
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	30.80%	28.10%	30.30%	29.60%
Customer Concentration Risk \| Sales Revenue, Net \| Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	17.30%	20.10%	17.60%	16.50%
Customer Concentration Risk \| Sales Revenue, Net \| Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	6.30%	13.50%	7.00%	9.80%
Number of federal government agencies \| agency				3
Minimum
Summary Of Significant Accounting Policies [Line Items]
SaaS Subscriptions contracts term			1 year
Term license subscription contracts term			1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
SaaS Subscriptions contracts term			3 years
Term license subscription contracts term			3 years
Computer software
Summary Of Significant Accounting Policies [Line Items]
Useful Life (in years)			3 years
Computer hardware
Summary Of Significant Accounting Policies [Line Items]
Useful Life (in years)			3 years
Equipment
Summary Of Significant Accounting Policies [Line Items]
Useful Life (in years)			5 years
Office furniture and fixtures
Summary Of Significant Accounting Policies [Line Items]
Useful Life (in years)			10 years

Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 42,328		$ 42,328		$ 15,007
Less: accumulated depreciation	(5,505)		(5,505)		(7,468)
Property and equipment, net	36,823		36,823		7,539
Depreciation and amortization expense	1,100	$ 700	1,900	$ 1,000
Loss on disposal of equipment	100		145	0
Capital leases	3,700		3,700
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	32,601		32,601		9,958
Disposal of property plant and equipment	3,200		3,200
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,956		3,956		2,535
Disposal of property plant and equipment		$ 100		$ 100
Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,910		3,910		649
Disposal of property plant and equipment	800		800
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,727		1,727		1,727
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 134		$ 134		$ 138

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued contract labor costs	$ 2,746	$ 3,128
Accrued leasehold improvement costs	2,406	0
Accrued hosting costs	1,914	579
Accrued reimbursable employee expenses	1,147	459
Accrued marketing and tradeshow expenses	812	229
Accrued computer hardware costs	670	0
Accrued audit and tax expenses	601	375
Accrued third party license fees	341	729
Other accrued expenses	1,438	1,965
Total	$ 12,075	$ 7,464

Debt - Additional Information (Detail) - USD ($)	1 Months Ended
Debt - Additional Information (Detail) - USD ($)	Nov. 30, 2017	Jun. 30, 2019
Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility	$ 20,000,000.0
Term Loan
Line of Credit Facility [Line Items]
Line of credit, outstanding borrowings		$ 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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Taxes [Line Items]
Effective tax rate	(3.00%)	(0.30%)	(1.50%)	(1.20%)
Net unrecognized tax benefits which would impact effective tax rate if recognized	$ 1.0		$ 1.0
Earliest Tax Year
Income Taxes [Line Items]
Open tax year			2015
Latest Tax Year
Income Taxes [Line Items]
Open tax year			2018
Minimum \| Subsidiaries
Income Taxes [Line Items]
Effective tax rate			0.00%
Maximum \| Subsidiaries
Income Taxes [Line Items]
Effective tax rate			32.00%

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended	6 Months Ended
	May 31, 2019	Nov. 30, 2018	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	May 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period for option exercise				5 years
Weighted average grant-date fair value (in usd per share)				$ 13.57
Vested in period, value				$ 1.5	$ 1.6
Compensation cost related to nonvested stock options not yet recognized				$ 10.9
Unrecognized compensation cost related to nonvested stock option recognized over weighted average period, in years				2 years 4 months 24 days
Stock option cancellation agreement, vested options to purchase (in shares)				700,000
Granted (in shares)				700,000
Exercise price of stock options granted (in usd per share)				$ 33.98
Service period (in years)			6 years 4 months 24 days	6 years 2 months 12 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested restricted stock units				$ 20.6
Weighted average remaining vesting period				2 years 3 months 18 days
Grant of RSUs (in shares)				126,065
Fair value of shares granted (in usd per share)				$ 35.02
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available to be issued (in shares)				4,913,160
2017 Equity Incentive Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of award at grant date		$ 7.7
Grant of RSUs (in shares)		255,930
Fair value of shares granted (in usd per share)		$ 30.06
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 (in shares)				7,084,603		6,421,442
2007 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available to be issued (in shares)						421,442
Number of shares available for grants (in shares)						0
Period for which options can be granted				10 years
Chief Executive Officer \| 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option cancellation agreement, vested options to purchase (in shares)	700,000
Granted (in shares)	700,000
Exercise price of stock options granted (in usd per share)	$ 33.98
Share price (in usd per share)	$ 84.63
Value of award at grant date	$ 9.5
Service period (in years)	2 years 7 months 6 days

Stock-Based Compensation - Assumptions Used to Estimate Fair Value of Stock Options (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Share-based Payment Arrangement [Abstract]
Risk-free interest rate	210.00%	210.00%
Expected term (in years)	2 years 7 months 6 days	2 years 7 months 6 days
Expected volatility	55.00%	55.00%
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Summary of the Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019
Number of Shares
January 1, 2019 (in shares)	5,021,068	5,021,068
Granted (in shares)		700,000
Exercised (in shares)		(630,296)
Canceled (in shares)		(44,140)
Outstanding at June 30, 2019 (in shares)		5,046,632
Exercisable at June 30, 2019 (in shares)		3,207,972
Weighted Average Exercise Price
January 1, 2019 (in usd per share)	$ 7.30	$ 7.30
Granted (in usd per share)		33.98
Exercised (in usd per share)		3.15
Canceled (in usd per share)		10.45
Outstanding at June 30, 2019 (in usd per share)		11.49
Exercisable at June 30, 2019 (in usd per share)		$ 7.12
Weighted Average Remaining Contractual Term (Years)
January 1, 2019	6 years 4 months 24 days	6 years 2 months 12 days
Outstanding at June 30, 2019	6 years 4 months 24 days	6 years 2 months 12 days
Exercisable at June 30, 2019		6 years
Aggregate Intrinsic Value (in thousands)
January 1, 2019	$ 97,440	$ 97,440
Exercised		18,852
Outstanding at June 30, 2019		124,021
Exercisable at June 30, 2019		$ 92,872

Stock-Based Compensation - Schedule of Restricted Stock Unit Activity (Detail) - Restricted Stock Units	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Number of Shares
Non-vested outstanding at January 1, 2019 (in shares) \| shares	1,175,049
Granted (in shares) \| shares	126,065
Vested (in shares) \| shares	(284,690)
Canceled (in shares) \| shares	(20,375)
Non-vested outstanding at June 30, 2019 (in shares) \| shares	996,049
Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2019 (in usd per share) \| $ / shares	$ 26.04
Fair value of shares granted (in usd per share) \| $ / shares	35.02
Vested (in usd per share) \| $ / shares	30.03
Canceled (in usd per share) \| $ / shares	28.70
Non-vested outstanding at June 30, 2019 (in usd per share) \| $ / shares	$ 25.99

Stock-Based Compensation - Schedule of Stock-based Compensation Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,689	$ 2,206	$ 9,914	$ 4,446
Subscriptions, Software, And Support
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	161	107	315	217
Professional Services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	244	203	2,218	423
Selling and Marketing Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	814	538	3,195	1,045
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	435	342	2,550	733
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,035	$ 1,016	$ 1,636	$ 2,028

Stockholders' Equity (Detail)	6 Months Ended
Stockholders' Equity (Detail)	Jun. 30, 2019 vote_per_share $ / shares shares	Dec. 31, 2018 shares
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001
Common stock, shares issued (in shares)	31,462,892	29,626,054
Common stock, shares outstanding (in shares)	31,462,892	29,626,054
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 (in shares)	100,000,000	100,000,000
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001
Common stock, shares issued (in shares)	33,374,676	34,290,383
Common stock, shares outstanding (in shares)	33,374,676	34,290,383
Number of votes entitled to stockholders per share \| vote_per_share	10

Commitments and Contingencies -Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Apr. 30, 2018
Debt Instrument [Line Items]
Total payments committed under operating lease	$ 91,349		$ 91,349			$ 87,200
Tenant improvement allowance, maximum	18,400		18,400
Deferred rent credit	1,400		1,400		$ 1,200
Deferred rent credit, net of current portion	16,000		16,000		14,400
Office furniture and fixtures acquired under capital lease agreements	3,700		3,700
Deferred rent, noncurrent	21,500		21,500		17,400
Total rent and lease expense	2,400	$ 1,800	5,500	$ 3,800
Payment of royalty fees			300
Outstanding letters of credit	$ 10,500		$ 10,500		$ 10,500
Letter of Credit
Debt Instrument [Line Items]
Letter of credit entered into in connection with lease						$ 9,400

Commitments and Contingencies - Future Minimum Lease Commitments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Apr. 30, 2018
Operating Leases
Remainder of 2019	$ 2,111
2020	3,375
2021	6,790
2022	6,938
2023	6,987
Thereafter	65,148
Total minimum lease payments	91,349	$ 87,200
Capital Leases
Remainder of 2019	663
2020	1,325
2021	1,325
2022	663
2023	0
Thereafter	0
Total minimum lease payments	3,976
Less: amounts representing interest	(302)
Present value of capital lease obligations	$ 3,674

Organization and Description of Business	6 Months Ended
Organization and Description of Business	Jun. 30, 2019
Accounting Policies [Abstract]
Organization and Description of Business	Organization and Description of BusinessAppian Corporation (together with its subsidiaries, “Appian,” the “Company,” “we” or “our”) provides a low-code software development platform that allows companies to rapidly build powerful business applications. The applications created on our platform help companies drive digital transformation and competitive differentiation. We were incorporated in the state of Delaware in August 1999. As of June 30, 2019, we were headquartered in Reston, Virginia and subsequently moved to Tysons, Virginia. We operate in Canada, Switzerland, the United Kingdom, France, Germany, the Netherlands, Italy, Australia, Spain, Singapore and Sweden.

Debt	6 Months Ended
Debt	Jun. 30, 2019
Debt Disclosure [Abstract]
Debt	DebtLine of CreditIn 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 June 30, 2019. As of June 30, 2019, we had no outstanding borrowings under the revolving line of credit.

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2019
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 32%. 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 six months ended June 30, 2019, the actual effective tax rates were (3.0)% and (1.5)%, respectively. For the three and six months ended June 30, 2018, the actual effective tax rates were (0.3)% and (1.2)%, respectively. We assess uncertain tax positions in accordance with ASC 740-10, Accounting for Uncertainties in Income Taxes. As of June 30, 2019, our net unrecognized tax benefits totaled $1.0 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 2015 through 2018 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.

Stockholders' Equity	6 Months Ended
Stockholders' Equity	Jun. 30, 2019
Equity [Abstract]
Stockholders' Equity	Stockholders’ EquityAs of June 30, 2019, we had authorized 500,000,000 shares of Class A common stock and 100,000,000 shares of Class B common stock, each with a par value of $0.0001 per share, of which 31,462,892 shares of Class A common stock and 33,374,676 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.

Segment and Geographic Information - Summary of Revenues By Geography (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 66,911	$ 59,883	$ 126,490	$ 111,579
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	46,295	43,035	88,178	78,560
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 20,616	$ 16,848	$ 38,312	$ 33,019

Segment and Geographic Information - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Sales Revenue, Net \| Geographic Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.50%	10.20%