Stock Plans - Summary of Option Activity under Plans and Related Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options Outstanding, Beginning balance		1,949,089
Number of Stock Options Outstanding, Granted	0	48,260
Number of Stock Options Outstanding, Exercised		(164,233)
Number of Stock Options Outstanding, Cancelled or forfeited		(151,215)
Number of Stock Options Outstanding, Ending balance	1,681,901	1,681,901	1,949,089
Number of Shares, Vested and expected to vest	1,539,544	1,539,544
Number of Shares, Exercisable	888,151	888,151
Weighted Average Exercise Price of Stock Options Outstanding	$ 39.36	$ 39.36	$ 39.27
Weighted Average Exercise Price, Granted		53.59
Weighted Average Exercise Price, Exercised		29.72
Weighted Average Exercise Price, Cancelled or forfeited		46.46
Weighted Average Exercise Price, Vested and expected to vest	39.24	39.24
Weighted Average Exercise Price, Exercisable	$ 35.74	$ 35.74
Weighted-Average Remaining Contractual Term (in years)		7 years 4 months 2 days	8 years 1 month 2 days
Weighted-Average Remaining Contractual Term (in years), Vested and expected to vest		7 years 3 months 4 days
Weighted-Average Remaining Contractual Term (in years), Exercisable		6 years 7 months 28 days
Aggregate Intrinsic Value	$ 25,899	$ 25,899	$ 47,480
Aggregate Intrinsic Value, Vested and expected to vest	24,647	24,647
Aggregate Intrinsic Value, Exercisable	$ 16,756	$ 16,756