Share-Based Compensation Stock Option Information Related to Equity Incentive Plan (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Options
Outstanding, beginning of period	1,514,159
Granted	249,303
Exercised	(330,898)
Forfeited	(37,676)
Outstanding, end of period	1,394,888
Vested and expected to vest, end of period	1,352,289
Exercisable, end of period	687,696
Weighted average exercise price
Outstanding, beginning of period	$ 55.27
Granted	$ 108.05
Exercised	$ 47.70
Forfeited	$ 72.45
Outstanding, end of period	$ 66.03
Vested and expected to vest, end of period	$ 65.35
Exercisable, end of period	$ 50.60
Weighted Average Remaining Contractual Life in Years
Outstanding, end of period	4 years 1 month 3 days
Vested and expected to vest, end of period	4 years 0 months 14 days
Exercisable, end of period	2 years 10 months 20 days
Aggregate Intrinsic Value of In-The-Money Options
Outstanding, end of period	$ 69,834,175
Vested and expected to vest, end of period	68,622,901
Exercisable, end of period	$ 45,022,407