Status of Stock Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Shares
Outstanding	4,731,483	4,249,168
Vested and expected to vest	4,543,051
Vested	2,341,265	2,341,265
Weighted-Average Exercise Price Per Share
Outstanding	$ 24.19	$ 14.77
Vested and expected to vest	23.73
Vested	$ 14.92
Remaining Contractual Life
Outstanding	7 years 3 months 18 days
Vested and expected to vest	7 years 2 months 12 days
Vested	5 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding	$ 128,996
Vested and expected to vest	125,964
Vested	$ 85,533