Treasury Stock (Details) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Oct. 31, 2013 Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount			$ 3,900,000,000		$ 500,000,000
Available to repurchase common stock			179,300,000
Amount expended on share repurchases in open market transactions	55,300,000	75,000,000	156,300,000	175,000,000
Number of shares repurchased	764,800	983,200	2,240,050	2,361,800
Average per share price on share repurchases in open market transactions	$ 72.30	$ 76.24	$ 69.79	$ 74.08
Number of shares withheld to satisfy minimum tax withholding obligations	43,035	31,733	389,369	227,604
Cash paid for tax withholding on vested stock awards	$ 2,900,000	$ 2,500,000	$ 27,708,000	$ 17,524,000