Stockholders' Equity Common Stock - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Number of shares, Beginning Balance	5,026,246
Number of Shares, Granted	1,695,125
Number of Shares, Exercised	(1,273,736)
Number of Shares, Forfeited	(378,502)
Number of shares, Ending Balance	5,069,133	5,026,246
Number of Shares, Options vested and expected to vest	5,069,133
Number of Shares, Options exercisable	1,686,284
Weighted Average Exercise Price, Beginning Balance	$ 8.01
Weighted Average Exercise Price, Granted	26.04
Weighted Average Exercise Price, Exercised	1.68
Weighted Average Exercise Price, Forfeited	24.93
Weighted Average Exercise Price, Ending Balance	14.36	$ 8.01
Weighted Average Exercise Price, Options vested and expected to vest	14.36
Weighted Average Exercise Price, Options exercisable	$ 8.05
Weighted Average Remaining Contractual Term, Outstanding	8 years 3 months 4 days	8 years 8 months 12 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest	8 years 3 months 4 days
Weighted Average Remaining Contractual Term, Options exercisable	7 years 7 months 13 days
Aggregate Intrinsic Value, Outstanding	$ 16,736	$ 136,945
Aggregate Intrinsic Value, Options vested and expected to vest	16,736
Aggregate Intrinsic Value, Options exercisable	$ 9,048