Earnings Per Share - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Options to purchase shares of common stock not included in the computation of diluted earnings per share	6.3	12.3
Repurchased shares of common stock	5.4
Average price per share	$ 73.18
Total cash outlay	$ 392,000,000
Amount authorized for share repurchase program	1,500,000,000
Amount remains authorized for future repurchases	$ 622,700,000
Expiration date of repurchase program	Dec. 31, 2014