Schedule of Information about All Outstanding Options (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number, Options Outstanding	7,897,451	7,620,958	7,436,238	7,558,945
Weighted average exercise price, Options Outstanding	$ 57.29	$ 43.63	$ 36.31	$ 31.63
Aggregate intrinsic value, Options Outstanding	$ 426,248,728
Weighted average remaining contractual life, Options Outstanding	2 years 10 months 24 days
Number, Options Exercisable	1,412,422
Weighted Average Exercise Price, Options Exercisable	$ 43.59
Aggregate intrinsic value, Options Exercisable	$ 95,577,868
Weighted average remaining contractual life, Options Exercisable	1 year 9 months 18 days