Stock-Based Compensation - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Options Outstanding
Beginning balance (in shares)	1,098,823
Granted (in shares)	65,522
Exercised (in shares)	(133,927)
Canceled (in shares)	(4,266)
Ending balance (in shares)	1,026,152	1,098,823
Exercisable at period end (in shares)	838,004
Weighted-Average Exercise Price per Share
Beginning balance (in dollars per share)	$ 35.39
Granted (in dollars per share)	87.09
Exercised (in dollars per share)	21.84
Canceled (in dollars per share)	72.91
Ending balance (in dollars per share)	40.30	$ 35.39
Exercisable (in dollars per share)	$ 32.15
Weighted-Average Remaining Contractual Life
Outstanding, weighted average remaining contractual life (in years)	4 years 1 month 7 days	4 years 3 months 20 days
Exercisable weighted average remaining contractual life (in years)	3 years 4 months 26 days
Aggregate Intrinsic Value
Beginning balance	$ 52,332
Granted	0
Exercised	7,220
Canceled	13
Ending balance	36,377	$ 52,332
Exercisable	$ 36,537