Share-Based Compensation - Stock Option Information Related to Equity Incentive Plan (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015
Options
Outstanding, beginning of period	1,394,888
Granted	6,718
Exercised	(140,880)
Forfeited	(12,400)
Outstanding, end of period	1,248,326
Vested and expected to vest, end of period	1,213,499
Exercisable, end of period	554,601
Weighted Average Exercise Price
Outstanding, beginning of period	$ 66.03
Granted	$ 120.46
Exercised	$ 48.97
Forfeited	$ 82.72
Outstanding, end of period	$ 68.08
Vested and expected to vest, end of period	$ 67.45
Exercisable, end of period	$ 51.32
Weighted Average Remaining Contractual Life in Years
Outstanding, end of period	4 years 22 days
Vested and expected to vest, end of period	4 years 4 days
Exercisable, end of period	2 years 10 months 2 days
Aggregate Intrinsic Value of In-The- Money Options
Outstanding, end of period	$ 73,596,215
Vested and expected to vest, end of period	72,313,282
Exercisable, end of period	$ 41,996,945