Share-Based Compensation - Stock Option Information Related to Equity Incentive Plan (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014
Options
Outstanding, beginning of period	1,514,159
Granted	229,476
Exercised	(160,652)
Forfeited	(13,654)
Outstanding, end of period	1,569,329
Vested and expected to vest, end of period	1,510,886
Exercisable, end of period	820,343
Weighted Average Exercise Price
Outstanding, beginning of period	$ 55.27
Granted	$ 108.30
Exercised	$ 46.96
Forfeited	$ 70.36
Outstanding, end of period	$ 63.74
Vested and expected to vest, end of period	$ 62.94
Exercisable, end of period	$ 50.28
Weighted Average Remaining Contractual Life in Years
Outstanding, end of period	4 years 4 months 18 days
Vested and expected to vest, end of period	4 years 3 months 25 days
Exercisable, end of period	3 years 3 months 10 days
Aggregate Intrinsic Value of In-The- Money Options
Outstanding, end of period	$ 83,017,236
Vested and expected to vest, end of period	81,128,378
Exercisable, end of period	$ 54,421,775