Background and Basis of Presentation Share Repurchase Program (Details) (USD $)	3 Months Ended		12 Months Ended	1 Months Ended		18 Months Ended	1 Months Ended		3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Oct. 31, 2012 October 2011 Share Repurchase Program [Member]	Oct. 31, 2011 October 2011 Share Repurchase Program [Member]	Mar. 31, 2013 October 2011 Share Repurchase Program [Member]	Aug. 31, 2013 April 2013 Share Repurchase Program [Member]	Apr. 30, 2013 April 2013 Share Repurchase Program [Member]	Mar. 31, 2014 April 2013 Share Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Planned share repurchase program				$ 1,500,000,000	$ 1,000,000,000		$ 1,000,000,000	$ 300,000,000
Repurchase of common stock, shares	7,500,000.0	1,700,000.0				48,300,000
Repurchases of common stock, value	272,000,000	57,000,000	600,000,000
Average price of repurchased shares, per share	$ 35.98	$ 34.05				$ 31.06
Amount remaining in the repurchase program									$ 185,000,000