Stock Based Awards - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	12 Months Ended
	May. 31, 2015	Feb. 28, 2009	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 20, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved				4,845,579	3,900,281
Common stock reserved for future issuance				1,350,543	991,401	9,533
Intrinsic value of stock option exercised				$ 1,400,000	$ 800,000	$ 0
Unrecognized employee stock-based compensation				$ 18,200,000
Weighted-average remaining vesting period				2 years 4 months 24 days
Unvested stock options expected to vest, term				8 years
Additional shares issued				1,091,045	2,531,915
Voting power per share				One
Recognized compensation expense				$ 10,699,000	$ 4,641,000	$ 215,000
Weighted Average Remaining Contractual Life, Options outstanding				8 years 1 month 6 days
Co-Founder And CEO [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Separation related costs	$ 2,400,000
Unexercised vested and expected to vest stock options	$ 2,000,000
Unvested stock options expected to vest, term	12 months
Incremental payroll costs			$ 400,000
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Stock options, weighted-average grant date fair value				$ 10.62	$ 16.90	$ 1.60
Tax benefits realized from options and other share-based payment arrangements				$ 0	$ 0	$ 0
Restricted stock units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Recognized compensation expense				1,600,000	$ 500,000	$ 0
Approximate compensation expenses				$ 2,900,000
Weighted Average Remaining Contractual Life, Options outstanding				2 years 7 months 6 days
2009 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period		4 years
Options vested , description				Options granted generally vest over four years and vest at a rate of 25% upon the first anniversary of the issuance date and 1/36th?per month thereafter
2014 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Options expiration period				10 years
Options vested , description				Options granted under the 2014 Plan have a contractual life of ten years and generally vest over four years and vest at a rate of 25% upon the first anniversary of the issuance date and 1/36th per month thereafter.
Number of shares reserved							4,100,000
Percentage of common stock issued and outstanding increase annually				4.50%
End date of automatic annual increase of shares reserved for issuance				Jan. 01, 2024
Common stock reserved for future issuance				1,350,543
2014 Plan [Member] | Incentive Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved				12,000,000
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved								150,000
Percentage of common stock issued and outstanding increase annually				1.00%
End date of automatic annual increase of shares reserved for issuance				Jan. 01, 2024
Additional shares issued				300,000
Voting power per share				Immediately after the grant would own stock possessing 5% or more of the total combined voting power or value of our common stock.
Percentage of stock possessing				5.00%
Rights to purchase stock that remains outstanding				$ 25,000
Offerings of purchase periods				27 months
Maximum employee subscription rate				15.00%
Maximum [Member] | 2009 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options expiration period		10 years
Minimum [Member] | 2009 Plan [Member] | Incentive Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				100.00%
Minimum [Member] | 2009 Plan [Member] | 10% Shareholders [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				110.00%
Minimum [Member] | 2014 Plan [Member] | Incentive Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				100.00%
Minimum [Member] | Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of options granted, percentage				85.00%