Stock-based Compensation Plans - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning balance, shares	41,939	42,059	40,027
Granted, shares	6,105	6,570	8,664
Exercised, shares	(8,269)	(5,168)	(4,171)
Forfeited, shares	(1,192)	(1,522)	(2,461)
Ending balance, shares	38,583	41,939	42,059
Beginning balance, Weighted-average exercise price	$ 70.33	$ 67.77	$ 63.84
Granted, Weighted-average exercise price	$ 99.04	$ 72.16	$ 72.04
Exercised, Weighted-average exercise price	$ 64.19	$ 51.73	$ 39.07
Forfeited, Weighted-average exercise price	$ 73.56	$ 70.57	$ 67.50
Ending balance, Weighted-average exercise price	$ 76.10	$ 70.33	$ 67.77