Stock-Based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2019
NUMBER OF SHARES
Beginning balance (in shares)	6,935,119
Granted (in shares)	914,790
Exercised (in shares)	(124,034)
Canceled (in shares)	(211,607)
Ending balance (in shares)	7,514,268
Options exercisable (in shares)	5,145,383
WEIGHTED AVERAGE EXERCISE PRICE
Beginning balance (in dollars per share)	$ 28.97
Granted (in dollars per share)	43.32
Exercised (in dollars per share)	30.94
Canceled (in dollars per share)	53.52
Ending balance (in dollars per share)	29.99
Options exercisable (in dollars per share)	$ 21.98
WEIGHTED AVERAGE REMAINING CONTRACTUAL LIFE (YEARS)
Options outstanding, weighted average remaining contractual life	6 years 7 months 6 days
Options exercisable, weighted average remaining contractual life	5 years 7 months 6 days
AGGREGATE INTRINSIC VALUE
Options outstanding	$ 63,671
Options exercisable	$ 61,881