Share-Based Compensation - Stock Option Information Related to Equity Incentive Plan (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014
Options
Outstanding, beginning of period	1,514,159
Granted	9,600
Exercised	(99,429)
Forfeited	(5,957)
Outstanding, end of period	1,418,373
Vested and expected to vest, end of period	1,380,441
Exercisable, end of period	587,639
Weighted Average Exercise Price
Outstanding, beginning of period	$ 55.27
Granted	$ 116.05
Exercised	$ 44.57
Forfeited	$ 66.22
Outstanding, end of period	$ 56.38
Vested and expected to vest, end of period	$ 56.05
Exercisable, end of period	$ 44.59
Weighted Average Remaining Contractual Life in Years
Outstanding, end of period	4 years 2 months 13 days
Vested and expected to vest, end of period	4 years 1 month 28 days
Exercisable, end of period	2 years 11 months 15 days
Aggregate Intrinsic Value of In-The- Money Options
Outstanding, end of period	$ 102,687,693
Vested and expected to vest, end of period	100,401,661
Exercisable, end of period	$ 49,473,911