Earnings Per Share - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Options to purchase shares of common stock not included in the computation of diluted earnings per share	11.9	13.8	12.3	12.7
Repurchased shares of common stock	1.5		5.5
Average price per share	$ 62.61		$ 62.29
Total cash outlay	$ 97,600,000		$ 345,700,000
Amount remains authorized for future repurchases			1,154,300,000
Amount authorized for share repurchase program			$ 1,500,000,000