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, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding, Beginning Balance	6,565	8,341	10,229
Shares, Granted	307	1,223	526
Shares, Exercised	(1,425)	(2,925)	(2,008)
Shares, Forfeited	(116)	(74)	(406)
Shares, Outstanding, Ending Balance	5,331	6,565	8,341
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 22.17	$ 15.51	$ 12.79
Shares, Vested and expected to vest	5,331
Weighted Average Exercise Price, Granted	$ 80.77	$ 36.94	$ 30.56
Weighted Average Exercise Price, Exercised	$ 21.13	$ 9.38	$ 4.51
Weighted Average Exercise Price, Forfeited	$ 28.68	$ 20.43	$ 20.96
Weighted Average Exercise Price, Outstanding, Ending balance	$ 25.68	$ 22.17	$ 15.51
Options Exercisable at End of Period, Outstanding, Beginning Balance	2,666	4,394	5,168
Weighted Average Exercise Price, Expected to vest	$ 25.68
Options Exercisable at End of Period, Outstanding, Ending Balance	2,589	2,666	4,394
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 14.71	$ 10.13	$ 6.06
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	$ 16.57	$ 14.71	$ 10.13
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 206,636	$ 119,802	$ 128,472
Weighted Average Fair Value of Options Granted During the Period, Granted	$ 23.00	$ 10.82	$ 9.72
Aggregate Intrinsic Value, Exercised	136,807	129,488	50,921
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 487,673	$ 206,636	$ 119,802