Share Based Compensation - Summary of Changes in Number of Shares of Common Stock Under Option (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares at begging of period (in shares)	5,003
Granted (in shares)	1,114
Exercised (in shares)	(4)
Forfeited (in shares)	(10)
Shares at end of period (in shares)	6,103
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning of period (in dollars per share)	$ 72.72
Weighted average exercise price, granted (in dollars per share)	115.14
Weighted average exercise price, exercised (in dollars per share)	106.83
Weighted average exercise price, forfeitures (in dollars per share)	155.65
Weighted average exercise price, end of period (in dollars per share)	$ 80.31
Expected to vest (in shares)	6,103
Weighted average exercise price, expected to vest (in dollars per share)	$ 80.31
Options exercisable at beginning of period (in shares)	3,011	2,545
Weighted average exercise price of exercisable options, beginning of period (in dollars per share)	$ 45.10	$ 26.82
Weighted average exercise price of granted options (in dollars per share)	$ 24.02
Aggregate intrinsic value	$ 417,748	$ 351,277