Schedule of Information about All Outstanding Options (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number, Options Outstanding	8,770,133	8,400,183	7,897,451	7,620,958
Weighted average exercise price, Options Outstanding	$ 99.06	$ 80.50	$ 57.29	$ 43.63
Aggregate intrinsic value, Options Outstanding	$ 128,620,135
Weighted average remaining contractual life, Options Outstanding	3 years
Number, Options Exercisable	2,074,867
Weighted Average Exercise Price, Options Exercisable	$ 78.58
Aggregate intrinsic value, Options Exercisable	$ 63,939,686
Weighted average remaining contractual life, Options Exercisable	2 years