Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	Apr. 29, 2019
Document and Entity Information [Line Items]
Entity Registrant Name	APPIAN CORP
Entity Central Index Key	0001441683
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Trading Symbol	APPN
Class A Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		31,325,029
Class B Common Stock
Document and Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		33,375,276

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 75,353	$ 94,930
Accounts receivable, net of allowance of $600 as of March 31, 2019 and December 31, 2018	81,012	79,383
Deferred commissions, current	15,095	14,020
Prepaid expenses and other current assets	20,262	21,293
Total current assets	191,722	209,626
Property and equipment, net	23,340	7,539
Deferred commissions, net of current portion	15,555	15,088
Deferred tax assets	328	326
Other assets	562	601
Total assets	231,507	233,180
Current liabilities
Accounts payable	6,364	9,249
Accrued expenses	12,111	7,464
Accrued compensation and related benefits	12,277	13,796
Deferred revenue, current	100,065	95,523
Other current liabilities	2,102	2,369
Total current liabilities	132,919	128,401
Deferred tax liabilities	41	42
Deferred revenue, net of current portion	14,990	16,145
Deferred rent, net of current portion	19,264	15,400
Total liabilities	167,214	159,988
Stockholders’ equity
Additional paid-in capital	226,582	218,284
Accumulated other comprehensive income	882	542
Accumulated deficit	(163,177)	(145,640)
Total stockholders’ equity	64,293	73,192
Total liabilities and stockholders’ equity	231,507	233,180
Class A Common Stock
Stockholders’ equity
Common stock	3	3
Class B Common Stock
Stockholders’ equity
Common stock	$ 3	$ 3

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 600	$ 600
Common stock, par value (in usd per share)	$ 0.0001
Class A Common Stock
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	30,882,834	29,626,054
Common stock, shares outstanding (in shares)	30,882,834	29,626,054
Class B Common Stock
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	33,798,188	34,290,383
Common stock, shares outstanding (in shares)	33,798,188	34,290,383

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Total revenue	$ 59,579	$ 51,696
Cost of revenue:
Total cost of revenue	24,066	21,049
Gross profit	35,513	30,647
Operating expenses:
Sales and marketing	29,945	22,964
Research and development	13,956	9,870
General and administrative	9,016	8,060
Total operating expenses	52,917	40,894
Operating loss	(17,404)	(10,247)
Other expense (income):
Other income, net	(60)	(918)
Interest expense	71	13
Total other expense (income)	11	(905)
Loss before income taxes	(17,415)	(9,342)
Income tax expense	122	211
Net loss	$ (17,537)	$ (9,553)
Net loss per share attributable to common stockholders:
Basic and diluted (in dollar per share)	$ (0.27)	$ (0.16)
Weighted average common shares outstanding:
Basic and diluted (in shares)	64,306,667	60,850,521
Subscriptions, Software, And Support
Revenue:
Total revenue	$ 34,909	$ 26,952
Cost of revenue:
Total cost of revenue	3,585	2,628
Professional Services
Revenue:
Total revenue	24,670	24,744
Cost of revenue:
Total cost of revenue	$ 20,481	$ 18,421

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (17,537)	$ (9,553)
Comprehensive loss, net of income taxes:
Foreign currency translation adjustment	340	(566)
Total other comprehensive loss, net of income taxes	$ (17,197)	$ (10,119)

CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		60,599,877
Beginning balance at Dec. 31, 2017	$ 45,524	$ 6	$ 141,268	$ 439	$ (96,189)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(9,553)				(9,553)
Issuance of common stock to directors (in shares)		2,935
Exercise of stock options (in shares)		607,349
Exercise of stock options	982		982
Stock-based compensation expense	2,240		2,240
Other comprehensive income	(565)			(565)
Ending balance (in shares) at Mar. 31, 2018		61,210,161
Ending balance at Mar. 31, 2018	38,628	$ 6	144,490	(126)	(105,742)
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	$ (17,537)				(17,537)
Issuance of common stock to directors (in shares)		3,461
Vesting of restricted stock units (in shares)		482,444
Exercise of stock options (in shares)	482,444	278,680
Exercise of stock options	$ 1,073		1,073
Stock-based compensation expense	7,225		7,225
Other comprehensive income	340			340
Ending balance (in shares) at Mar. 31, 2019		64,681,022
Ending balance at Mar. 31, 2019	$ 64,293	$ 6	$ 226,582	$ 882	$ (163,177)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (17,537)	$ (9,553)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	798	268
Deferred income taxes	(3)	76
Stock-based compensation	7,225	2,240
Changes in assets and liabilities:
Accounts receivable	(1,702)	1,932
Prepaid expenses and other assets	1,252	(1,085)
Deferred commissions	(1,542)	315
Accounts payable and accrued expenses	1,577	(2,161)
Accrued compensation and related benefits	(1,485)	(2,743)
Other current liabilities	(138)	909
Deferred revenue	3,718	(3,849)
Deferred rent, non-current	3,698	(182)
Net cash used in operating activities	(4,139)	(13,833)
Cash flows from investing activities:
Purchases of property and equipment	(16,595)	(1,036)
Net cash used in investing activities	(16,595)	(1,036)
Cash flows from financing activities:
Proceeds from exercise of common stock options	1,073	983
Net cash provided by financing activities	1,073	983
Effect of foreign exchange rate changes on cash and cash equivalents	84	1,004
Net decrease in cash and cash equivalents	(19,577)	(12,882)
Cash and cash equivalents, beginning of period	94,930	73,758
Cash and cash equivalents, end of period	75,353	60,876
Supplemental disclosure of cash flow information:
Cash paid for interest	69	8
Cash paid for income taxes	$ 43	$ 57

Organization and Description of Business	3 Months Ended
Organization and Description of Business	Mar. 31, 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. We are headquartered in Reston, Virginia and operate in Canada, Switzerland, the United Kingdom, France, Germany, the Netherlands, Italy, Australia, Spain, Singapore and Sweden.

Significant Accounting Policies	3 Months Ended
Significant Accounting Policies	Mar. 31, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	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 and, to a lesser degree, non-user based single application licenses. We bill customers and collect payment for subscriptions to our platform in advance on a monthly, quarterly or annual basis. In certain instances, we have had customers pay their entire contract up front. SaaS Subscriptions Our SaaS subscription revenue is derived from customers accessing our cloud offering pursuant to contracts that are generally one to five years in length. We perform all required maintenance and support for our cloud offering and we do not separately charge customers for hosting costs. In these arrangements, our customers do not have the right to take the software on-premises and, as a result, such arrangements are not accounted for within the scope of the software revenue guidance. Revenue from SaaS subscriptions is recognized ratably over the term of the subscription, beginning with the date our service is made available to our customer. Term License Subscriptions Our term license subscription revenue is derived from customers with on-premises installations of our platform pursuant to contracts that are generally one to five years in length. Customers with term license subscriptions have the right to use our software and receive maintenance and support. Since we do not sell maintenance and support separately from the subscription, revenue for the term license subscription and maintenance and support is recognized ratably over the term of the subscription, upon delivery of the platform to the customer when sold on a standalone basis. 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 17.9% and 12.3% of our revenue for the three months ended March 31, 2019 and 2018, respectively, of which the top three federal government agencies generated 7.9% and 6.4% of our revenue for the three months ended March 31, 2019 and 2018, respectively. Additionally, 29.7% and 33.3% of our revenue during the three months ended March 31, 2019 and 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 March 31, 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. As of March 31, 2019, our non-trade receivables related entirely to a receivable from our tenant improvement allowance. The tenant improvement allowance receivable was $12.5 million and $14.4 million as of March 31, 2019 and December 31, 2018, respectively, 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 $4.4 million and $2.7 million for the three months ended March 31, 2019 and 2018, respectively. Fair Value of Financial Instruments The carrying amounts of our cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate fair value as of March 31, 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 months ended March 31, 2019 and 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 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”). 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 months ended March 31, 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 months ended March 31, 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. If we 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. If the share price of our Class A common stock closes on June 28, 2019, at or above the price it has traded at since June 30, 2018, we will lose "emerging growth company status" effective 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.

Debt	3 Months Ended
Debt	Mar. 31, 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 March 31, 2019. As of March 31, 2019, we had no outstanding borrowings under the revolving line of credit.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 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 33%. Fluctuations in the distribution of pre-tax income among our operating subsidiaries can lead to fluctuations of the effective tax rate in the condensed consolidated financial statements. For the three months ended March 31, 2019 and 2018, the actual effective tax rates were (0.7)% and (0.6)%, respectively. We assess uncertain tax positions in accordance with Accounting Standards Codification 740-10, Accounting for Uncertainties in Income Taxes. As of March 31, 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.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2019

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

Stock-Based Compensation

In May 2017, our board of directors adopted, and our stockholders approved, the 2017 Equity Incentive Plan (the “2017 Plan”), which became effective as of the date of the final prospectus for our 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 March 31, 2019, there were 7,072,843 shares of Class A common stock reserved for issuance under the 2017 Plan, of which 5,642,988 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 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.

We did not grant any stock options during the three months ended March 31, 2019 or 2018.

Stock Options

The following table summarizes the stock option activity for the three months ended March 31, 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	—	—
Exercised	(482,444)	2.28			14,600
Canceled	(32,380)	10.60
Outstanding at March 31, 2019	4,506,244	7.82		6.6	119,919
Exercisable at March 31, 2019	3,053,424	6.89		6.2	84,097

The total fair value of stock options that vested during each of the three months ended March 31, 2019 and 2018 was $0.3 million. As of March 31, 2019, the total compensation cost related to unvested stock options not yet recognized was $2.1 million, which will be recognized over a weighted average period of 2.0 years.

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

Restricted Stock Units

The following table summarizes the restricted stock unit activity for the three months ended March 31, 2019:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2019	1,175,049	$	26.04
Granted	79,475	35.77
Vested	(278,680)	30.09
Canceled	(12,789)	28.34
Non-vested outstanding at March 31, 2019	963,055	25.65

As of March 31, 2019, total unrecognized compensation cost related to unvested restricted stock units was approximately $21.1 million, which will be recognized over a weighted average period of 2.4 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 three of 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 months ended March 31, 2019 and 2018 (in thousands):


	Three Months Ended March 31,
	2019		2018
Stock-based compensation expense related to restricted stock units	$	6,769	$	894
Stock-based compensation expense related to stock options	364		1,254
Stock-based compensation expense related to the issuance of common stock to directors	92		92
Total stock-based compensation expense	$	7,225	$	2,240

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 months ended March 31, 2019 and 2018 (in thousands):


	Three Months Ended March 31,
	2019		2018
Cost of revenue
Subscriptions, software and support	$	154	$	110
Professional services	1,974		220
Operating expenses
Sales and marketing	2,381		507
Research and development	2,115		391
General and administrative	601		1,012
Total stock-based compensation expense	$	7,225	$	2,240

Stockholders' Equity	3 Months Ended
Stockholders' Equity	Mar. 31, 2019
Equity [Abstract]
Stockholders' Equity	Stockholders’ EquityAs of March 31, 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 30,882,834 shares of Class A common stock and 33,798,188 shares of Class B common stock were issued and outstanding. The rights of the holders of Class A common stock and Class B common stock are identical, except with respect to voting and conversion rights. The holders of Class A common stock are entitled to one vote per share, and the holders of Class B common stock are entitled to ten votes per share, on all matters that are subject to stockholder vote. The holders of Class B common stock also have approval rights for certain corporate actions. Each share of Class B common stock may be converted into one share of Class A common stock at the option of its holder and will be automatically converted into one share of Class A common stock upon transfer thereof, subject to certain exceptions. In addition, upon the date on which the outstanding shares of Class B common stock represent less than 10% of the aggregate voting power of our capital stock, all outstanding shares of Class B common stock shall convert automatically into Class A common stock.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

We lease office space and equipment in our headquarters location in Reston, Virginia, as well as in the United Kingdom, France, Germany, Canada, Italy, Australia, the Netherlands, Singapore and Spain, 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 March 31, 2019, $1.4 million was included in other current liabilities and $16.4 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.

Lease Related Commitments

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

A summary of our future minimum lease commitments and other commitments by year as of March 31, 2019 is as follows (in thousands):


	Office Leases		Equipment Leases		Lease Related Commitments
Remainder of 2019	$	5,269	$	142	$	15,807
2020	6,380		22		—
2021	8,339		—		—
2022	6,948		—		—
2023	6,992		—		—
Thereafter	65,169		—		—
	99,097		164		15,807
Less: tenant improvement allowance	—		—		(12,498)
Total	$	99,097	$	164	$	3,309

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 March 31, 2019 and December 31, 2018, deferred rent totaled $21.1 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 $3.1 million and $2.1 million for the three months ended March 31, 2019 and 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 March 31, 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 4.

Legal

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

Segment and Geographic Information

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Segment and Geographic Information

The following table summarizes revenue by geography for the three months ended March 31, 2019 and 2018 (in thousands):


	Three Months Ended March 31,
	2019		2018
Domestic	$	41,883	$	34,481
International	17,696		17,215
Total	$	59,579	$	51,696

With respect to geographic information, revenue is attributed to respective geographies based on the contracting address of the customer. There were no individual foreign countries from which more than 10% of our total revenue was attributable for the three months ended March 31, 2019. Revenues from external customers attributed to the United Kingdom were 10.6% of our total revenue for the three months ended March 31, 2018. Substantially all of our long-lived assets were held in the United States as of March 31, 2019 and December 31, 2018.

Significant Accounting Policies (Policies)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 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 and, to a lesser degree, non-user based single application licenses. We bill customers and collect payment for subscriptions to our platform in advance on a monthly, quarterly or annual basis. In certain instances, we have had customers pay their entire contract up front. SaaS Subscriptions Our SaaS subscription revenue is derived from customers accessing our cloud offering pursuant to contracts that are generally one to five years in length. We perform all required maintenance and support for our cloud offering and we do not separately charge customers for hosting costs. In these arrangements, our customers do not have the right to take the software on-premises and, as a result, such arrangements are not accounted for within the scope of the software revenue guidance. Revenue from SaaS subscriptions is recognized ratably over the term of the subscription, beginning with the date our service is made available to our customer. Term License Subscriptions Our term license subscription revenue is derived from customers with on-premises installations of our platform pursuant to contracts that are generally one to five years in length. Customers with term license subscriptions have the right to use our software and receive maintenance and support. Since we do not sell maintenance and support separately from the subscription, revenue for the term license subscription and maintenance and support is recognized ratably over the term of the subscription, upon delivery of the platform to the customer when sold on a standalone basis. 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	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 March 31, 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. As of March 31, 2019, our non-trade receivables related entirely to a receivable from our tenant improvement allowance. The tenant improvement allowance receivable was $12.5 million and $14.4 million as of March 31, 2019 and December 31, 2018, respectively, 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. Commission expense was $4.4 million and $2.7 million for the three months ended March 31, 2019 and 2018, respectively.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of our cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate fair value as of March 31, 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 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 Status We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act (the “JOBS Act”). The JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. Thus, an emerging growth company can delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. We have elected to avail ourselves of this extended transition period and, as a result, we will not adopt new or revised accounting standards on the relevant dates on which adoption of such standards is required for other public companies.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted 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 months ended March 31, 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 months ended March 31, 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. If we 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. If the share price of our Class A common stock closes on June 28, 2019, at or above the price it has traded at since June 30, 2018, we will lose "emerging growth company status" effective 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.

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

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

Summary of the Stock Option Activity

The following table summarizes the stock option activity for the three months ended March 31, 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	—	—
Exercised	(482,444)	2.28			14,600
Canceled	(32,380)	10.60
Outstanding at March 31, 2019	4,506,244	7.82		6.6	119,919
Exercisable at March 31, 2019	3,053,424	6.89		6.2	84,097

Schedule of Restricted Stock Unit Activity

The following table summarizes the restricted stock unit activity for the three months ended March 31, 2019:


	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2019	1,175,049	$	26.04
Granted	79,475	35.77
Vested	(278,680)	30.09
Canceled	(12,789)	28.34
Non-vested outstanding at March 31, 2019	963,055	25.65

Schedule of Components of Stock-based Compensation Expense

The following table summarizes the components of our stock-based compensation expense for the three months ended March 31, 2019 and 2018 (in thousands):


	Three Months Ended March 31,
	2019		2018
Stock-based compensation expense related to restricted stock units	$	6,769	$	894
Stock-based compensation expense related to stock options	364		1,254
Stock-based compensation expense related to the issuance of common stock to directors	92		92
Total stock-based compensation expense	$	7,225	$	2,240

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


	Three Months Ended March 31,
	2019		2018
Cost of revenue
Subscriptions, software and support	$	154	$	110
Professional services	1,974		220
Operating expenses
Sales and marketing	2,381		507
Research and development	2,115		391
General and administrative	601		1,012
Total stock-based compensation expense	$	7,225	$	2,240

Basic and Diluted Loss per Common Share (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Summary of Securities Excluded From Calculation of Weighted Average Common Shares

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


	Three Months Ended March 31,
	2019	2018
Stock options	4,506,244	6,367,978
Restricted stock units	963,055	849,550

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases

A summary of our future minimum lease commitments and other commitments by year as of March 31, 2019 is as follows (in thousands):


	Office Leases		Equipment Leases		Lease Related Commitments
Remainder of 2019	$	5,269	$	142	$	15,807
2020	6,380		22		—
2021	8,339		—		—
2022	6,948		—		—
2023	6,992		—		—
Thereafter	65,169		—		—
	99,097		164		15,807
Less: tenant improvement allowance	—		—		(12,498)
Total	$	99,097	$	164	$	3,309

Segment and Geographic Information (Tables)

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Summary of Revenue By Geography

The following table summarizes revenue by geography for the three months ended March 31, 2019 and 2018 (in thousands):


	Three Months Ended March 31,
	2019		2018
Domestic	$	41,883	$	34,481
International	17,696		17,215
Total	$	59,579	$	51,696

Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Mar. 31, 2019 USD ($) agency	Mar. 31, 2018 USD ($)	Sep. 30, 2018	Feb. 28, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Percentage of license revenue (less than)		100.00%
Change in allowance for doubtful accounts	$ 0
Tenant improvement allowance receivable	12,500,000				$ 14,400,000	$ 15,800,000
Additional tenant improvement receivable				$ 2,600,000
Commission expense	$ 4,400,000	$ 2,700,000
Customer Concentration Risk \| Sales Revenue, Net \| Foreign Customers
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	29.70%	33.30%
Customer Concentration Risk \| Sales Revenue, Net \| Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	17.90%	12.30%
Customer Concentration Risk \| Sales Revenue, Net \| Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	7.90%	6.40%
Number of federal government agencies \| agency	3
Minimum
Summary Of Significant Accounting Policies [Line Items]
SaaS Subscriptions contracts term	1 year		1 year
Term license subscription contracts term	1 year		1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
SaaS Subscriptions contracts term	5 years
Term license subscription contracts term	5 years

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued leasehold improvement costs	$ 4,616	$ 0
Accrued contract labor costs	3,370	3,128
Accrued hosting costs	1,120	579
Accrued reimbursable employee expenses	551	459
Accrued audit and tax expenses	499	375
Accrued third party license fees	428	729
Accrued marketing and tradeshow expenses	297	229
Other accrued expenses	1,230	1,965
Total	$ 12,111	$ 7,464

Debt - Additional Information (Detail) - USD ($)	1 Months Ended
Debt - Additional Information (Detail) - USD ($)	Nov. 30, 2017	Mar. 31, 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
	Mar. 31, 2019	Mar. 31, 2018
Income Taxes [Line Items]
Effective tax rate	(0.70%)	(0.60%)
Net unrecognized tax benefits which would impact effective tax rate if recognized	$ 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	33.00%

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended
	Dec. 31, 2018	Nov. 30, 2018	Mar. 31, 2019	Mar. 31, 2018	May 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period for option exercise			5 years
Vested (in shares)			$ 0.3	$ 0.3
Compensation cost related to nonvested stock options not yet recognized			$ 2.1
Unrecognized compensation cost related to nonvested stock option recognized over weighted average period, in years			2 years
Stock option cancellation agreement, vested options to purchase (in shares)			0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested restricted stock units			$ 21.1
Weighted average remaining vesting period			2 years 4 months 24 days
Granted (in shares)			79,475
Fair value of shares granted (in usd per share)			$ 35.77
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available to be issued (in shares)			5,642,988
2017 Equity Incentive Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		255,930
Fair value of shares granted (in usd per share)		$ 30.06
Value of RSUs at grant date		$ 7.7
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)			7,072,843		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 \| 2007 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option cancellation agreement, vested options to purchase (in shares)	383,897

Stock-Based Compensation - Summary of the Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Number of Shares
January 1, 2019 (in shares)	5,021,068
Granted (in shares)	0
Exercised (in shares)	(482,444)
Canceled (in shares)	(32,380)
Outstanding at March 31, 2019 (in shares)	4,506,244	5,021,068
Exercisable at March 31, 2019 (in shares)	3,053,424
Weighted Average Exercise Price
January 1, 2019 (in usd per share)	$ 7.30
Granted (in usd per share)	0
Exercised (in usd per share)	2.28
Canceled (in usd per share)	10.60
Outstanding at March 31, 2019 (in usd per share)	7.82	$ 7.30
Exercisable at March 31, 2019 (in usd per share)	$ 6.89
Weighted Average Remaining Contractual Term (Years)
January 1, 2019	6 years 7 months 6 days	6 years 4 months 24 days
Outstanding at March 31, 2019	6 years 7 months 6 days	6 years 4 months 24 days
Exercisable at March 31, 2019	6 years 2 months 12 days
Aggregate Intrinsic Value (in thousands)
January 1, 2019	$ 97,440
Exercised	14,600
Outstanding at January 1, 2019	119,919	$ 97,440
Exercisable at March 31, 2019	$ 84,097

Stock-Based Compensation - Schedule of Restricted Stock Unit Activity (Detail) - Restricted Stock Units	3 Months Ended
	Mar. 31, 2019 $ / shares shares
Number of Shares
Non-vested outstanding at January 1, 2019 (in shares) \| shares	1,175,049
Granted (in shares) \| shares	79,475
Vested (in shares) \| shares	(278,680)
Canceled (in shares) \| shares	(12,789)
Non-vested outstanding at March 31, 2019 (in shares) \| shares	963,055
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	35.77
Vested (in usd per share) \| $ / shares	30.09
Canceled (in usd per share) \| $ / shares	28.34
Non-vested outstanding at March 31, 2019 (in usd per share) \| $ / shares	$ 25.65

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 7,225	$ 2,240
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	6,769	894
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	364	1,254
Issuance Of Common Stock To Directors
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 92	$ 92

Stock-Based Compensation - Schedule of Stock-based Compensation Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 7,225	$ 2,240
Subscriptions, Software, And Support
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	154	110
Professional Services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,974	220
Selling and Marketing Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	2,381	507
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	2,115	391
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 601	$ 1,012

Stockholders' Equity (Detail)	3 Months Ended
Stockholders' Equity (Detail)	Mar. 31, 2019 vote_per_share $ / shares shares	Dec. 31, 2018 $ / shares shares	Sep. 30, 2018 shares
Class of Stock [Line Items]
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued (in shares)	30,882,834	29,626,054
Common stock, shares outstanding (in shares)	30,882,834	29,626,054	30,882,834
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	$ 0.0001
Common stock, shares issued (in shares)	33,798,188	34,290,383
Common stock, shares outstanding (in shares)	33,798,188	34,290,383	33,798,188
Number of votes entitled to stockholders per share \| vote_per_share	10

Basic and Diluted Loss per Common Share - Summary of Securities Excluded From Calculation of Weighted Average Common Shares Outstanding (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	4,506,244	6,367,978
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible preferred stock (in shares)	963,055	849,550

Commitments and Contingencies -Narrative (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Apr. 30, 2018
Debt Instrument [Line Items]
Operating Leases, Future Minimum Payments Due				$ 87.2
Tenant improvement allowance, maximum	$ 18.4
Deferred rent credit	1.4		$ 1.2
Deferred rent credit, net of current portion	16.4		14.4
Deferred rent, noncurrent	21.1		17.4
Total rent and lease expense	3.1	$ 2.1
Payment of royalty fees	0.3
Outstanding letters of credit	$ 10.5		$ 10.5
Letter of Credit
Debt Instrument [Line Items]
Letter of credit entered into in connection with lease				$ 9.4

Commitments and Contingencies - Future Minimum Lease Commitments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Apr. 30, 2018
Operating Leased Assets [Line Items]
Total		$ 87,200
Office Leases
Operating Leased Assets [Line Items]
Remainder of 2019	$ 5,269
2020	6,380
2021	8,339
2022	6,948
2023	6,992
Thereafter	65,169
Total operating lease payments	99,097
Less: tenant improvement allowance	0
Total	99,097
Equipment Leases
Operating Leased Assets [Line Items]
Remainder of 2019	142
2020	22
2021	0
2022	0
2023	0
Thereafter	0
Total operating lease payments	164
Less: tenant improvement allowance	0
Total	164
Lease Related Commitments
Operating Leased Assets [Line Items]
Remainder of 2019	15,807
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total operating lease payments	15,807
Less: tenant improvement allowance	(12,498)
Total	$ 3,309

Segment and Geographic Information - Summary of Revenues By Geography (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 59,579	$ 51,696
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	41,883	34,481
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 17,696	$ 17,215

Segment and Geographic Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Sales Revenue, Net \| Geographic Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%	10.60%