Stockholders' Equity - Additional Information (Detail) - USD ($)			1 Months Ended			3 Months Ended	12 Months Ended			15 Months Ended
	May. 12, 2015	Mar. 31, 2015	Oct. 31, 2015	May. 31, 2015	Apr. 30, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Mar. 01, 2016	Apr. 25, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Convertible preferred stock, Issuance costs								$ 999,000
Common stock, shares authorized						95,500,000	150,000,000	95,500,000
Preferred stock, shares authorized						75,772,871		75,772,871
Number of common stock shares reserved for issuance						11,053,954	4,766,580	11,053,954
Weighted average grant date fair value of stock options granted							$ 11.29	$ 10.18	$ 3.42
Aggregate intrinsic value of stock options exercised							$ 1,900,000	$ 400,000	$ 47,000
Unrecognized share based compensation expense related to unvested stock options							$ 12,700,000
Unrecognized cost expected to be recognized over a weighted average period							2 years 10 months 24 days
Number of Outstanding Options, Granted							1,715,028
Stock-based compensation							$ 4,856,000	1,791,000	$ 155,000
Performance Options Without Market Condition [Member] | Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental share based compensation costs						$ 700,000
Share based compensation expense recognized								$ 600,000
Performance Options with Market Condition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period			4 years
Weighted average grant date fair value of stock options granted			$ 4.23
Number of Outstanding Options, Granted			169,402
Performance options with market condition, exercise price			$ 10.24
Achievement of specified performance goals year and month			2017-10
Requisite service period			5 years
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term for stock option plan grant							10 years
Options vesting period			4 years				4 years			6 years
Number of common stock shares reserved for issuance						180,190	984,357	180,190
Number of Outstanding Options, Granted			931,749
Stock-based compensation							$ 800,000
2015 ESPP Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares reserved for issuance							227,623
401 (k) Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Policy approved month and year							2015-04
Date of Policy beginning							Jun. 01, 2015
Percentage of match employee contribution							50.00%
Percentage of participants's annual salary							6.00%
Discretionary contribution							$ 100,000
Amended and Restated [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, after increase in authorized shares		185,000,000
Preferred stock, after increase in authorized shares		143,939,765
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of redeemable convertible preferred stock in connection with IPO, Shares							16,279,859
Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Convertible preferred stock, shares issued						73,487,415	0	73,487,415
Conversion of redeemable convertible preferred stock in connection with IPO, Shares							(141,654,309)
Preferred stock, shares authorized						75,772,871	7,285,456	75,772,871
Number of common stock shares reserved for issuance						9,238,868		9,238,868
IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized	150,000,000			150,000,000
Preferred stock, shares authorized	7,285,456			7,285,456
IPO [Member] | 2015 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effective date of plan							May 06, 2015
Number of common stock shares reserved for issuance					1,574,566							1,574,566
Stock option grants description							The number of shares reserved and available for issuance under the 2015 Plan will automatically increase each January 1, beginning on January 1, 2016 and thereafter until January 1, 2019, by the lesser of (i) 1,840,000 shares, (ii) 4% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31 or (iii) an amount determined by the Company’s board of directors.
Percentage threshold of outstanding shares as of December 31 of each year for calculation of annual increase in authorized shares under the plan					4.00%
IPO [Member] | 2015 Stock Option and Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in shares authorized under plan, shares threshold					1,840,000
IPO [Member] | 2015 ESPP Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effective date of plan							May 06, 2015
Number of common stock shares reserved for issuance					227,623							227,623
Percentage threshold of outstanding shares as of December 31 of each year for calculation of annual increase in authorized shares under the plan					100.00%
IPO [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of redeemable convertible preferred stock in connection with IPO, Shares	16,279,859			16,279,859
Warrants issued upon conversion	25,970			25,970
IPO [Member] | Series E redeemable convertible preferred stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Convertible preferred stock, shares issued		68,166,894
Convertible preferred stock, purchase price		$ 1.119
Convertible preferred stock, total cash consideration		$ 76,300,000
Convertible preferred stock, Issuance costs		$ 600,000
Conversion of convertible preferred stock to common stock		0.12572
Conversion of redeemable convertible preferred stock in connection with IPO, Shares	7,040,991
IPO [Member] | Series E redeemable convertible preferred stock [Member] | Scenario Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of convertible preferred stock to common stock											0.10329
IPO [Member] | Undesignated Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares authorized				5,000,000
IPO [Member] | Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued upon conversion	206,581			206,581