Stock-Based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2020
NUMBER OF SHARES
Beginning balance (in shares)	8,425,551
Granted (in shares)	868,620
Exercised (in shares)	(58,676)
Canceled (in shares)	(445,310)
Ending balance (in shares)	8,790,185
Options exercisable (in shares)	6,117,232
WEIGHTED AVERAGE EXERCISE PRICE
Beginning balance (in dollars per share)	$ 29.06
Granted (in dollars per share)	16.87
Exercised (in dollars per share)	5.28
Canceled (in dollars per share)	41.59
Ending balance (in dollars per share)	27.38
Options exercisable (in dollars per share)	$ 25.98
WEIGHTED AVERAGE REMAINING CONTRACTUAL LIFE (YEARS)
Options outstanding, weighted average remaining contractual life	6 years 2 months 12 days
Options exercisable, weighted average remaining contractual life	5 years 1 month 6 days
AGGREGATE INTRINSIC VALUE
Options outstanding	$ 12,418
Options exercisable	$ 12,418