Treasury Stock (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Equity [Abstract]
Stock repurchase program, authorized amount			$ 3,400,000,000
Available to repurchase common stock			234,600,000
Amount expended on share repurchases in open market transactions	39,700,000	0	101,000,000	100,000,000
Number of shares repurchased	614,750	0	1,475,250	1,378,600
Average per share price on share repurchases in open market transactions	$ 64.53		$ 68.49	$ 72.53
Number of shares withheld to satisfy minimum tax withholding obligations	23,796	12,821	346,334	195,871
Cash paid for tax withholding on vested stock awards	$ 1,600,000	$ 1,000,000	$ 24,804,000	$ 15,062,000