Share Repurchase Program (Narrative) (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	2 Months Ended	12 Months Ended		26 Months Ended
	Feb. 28, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 28, 2013
Share Repurchase Program
Increase in authorized amount		$ 500,000,000
Cumulative authorized amount		3,000,000,000
Authorization effective period		3 years
Common stock repurchased, shares	2,100	16,201	15,877	34,100
Common stock repurchased, average price per share	$ 90.09	$ 89.20	$ 61.49	$ 76.37
Common stock repurchased, value	185,600,000	1,445,044,000	976,322,000	2,600,000,000
Remaining balance under share repurchase program		$ 578,600,000