Stock-based Compensation - Schedule of Stock Options Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
NUMBER OF SHARES
Beginning balance (in shares) | shares	5,255,930
Granted (in shares) | shares	1,203,459
Exercised (in shares) | shares	(202,134)
Canceled (in shares) | shares	(19,296)
Ending balance (in shares) | shares	6,237,959
Options exercisable (in shares) | shares	3,954,715
WEIGHTED AVERAGE EXERCISE PRICE
Beginning balance (in dollars per share) | $ / shares	$ 14.34
Granted (in dollars per share) | $ / shares	46.30
Exercised (in dollars per share) | $ / shares	11.05
Cancelled (in dollars per share) | $ / shares	32.82
Ending balance (in dollars per share) | $ / shares	20.56
Options exercisable (in dollars per share) | $ / shares	$ 12.57
WEIGHTED AVERAGE REMAINING CONTRACTUAL LIFE (YEARS)
Options outstanding, weighted average remaining contractual life (in years)	7 years 3 months 1 day
Options exercisable (in years)	6 years 4 months 16 days
AGGREGATE INTRINSIC VALUE
Options outstanding | $	$ 176,569
Options exercisable | $	$ 142,558