Share Based Compensation - Summary of Changes in Number of Shares of Common Stock Under Option (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Outstanding, Beginning Balance	5,331	6,565	8,341
Shares, Granted	1,544	307	1,223
Shares, Exercised	(1,429)	(1,425)	(2,925)
Shares, Forfeited	(315)	(116)	(74)
Shares, Outstanding, Ending Balance	5,131	5,331	6,565
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 25.68	$ 22.17	$ 15.51
Shares, Vested and expected to vest	5,131
Weighted Average Exercise Price, Granted	$ 135.16	$ 80.77	$ 36.94
Weighted Average Exercise Price, Exercised	$ 20.75	$ 21.13	$ 9.38
Weighted Average Exercise Price, Forfeited	$ 41.72	$ 28.68	$ 20.43
Weighted Average Exercise Price, Outstanding, Ending balance	$ 58.71	$ 25.68	$ 22.17
Options Exercisable at End of Year, Outstanding, Beginning Balance	2,589	2,666	4,394
Weighted Average Exercise Price, Expected to vest	$ 58.71
Options Exercisable at End of Year, Outstanding, Ending Balance	2,370	2,589	2,666
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 16.57	$ 14.71	$ 10.13
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	$ 21.75	$ 16.57	$ 14.71
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 487,673	$ 206,636	$ 119,802
Weighted Average Fair Value of Options Granted During the Year, Granted	$ 42.77	$ 23.00	$ 10.82
Aggregate Intrinsic Value, Exercised	182,904	136,807	129,488
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 461,770	$ 487,673	$ 206,636