Schedule of Information about All Outstanding Options (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number, Options Outstanding	8,400,183	7,897,451	7,620,958	7,436,238
Weighted average exercise price, Options Outstanding	$ 80.50	$ 57.29	$ 43.63	$ 36.31
Aggregate intrinsic value, Options Outstanding	$ 328,564,543
Weighted average remaining contractual life, Options Outstanding	3 years
Number, Options Exercisable	1,671,216
Weighted Average Exercise Price, Options Exercisable	$ 52.19
Aggregate intrinsic value, Options Exercisable	$ 112,466,544
Weighted average remaining contractual life, Options Exercisable	1 year 10 months 24 days