Subsequent Events (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended	24 Months Ended	27 Months Ended	30 Months Ended	1 Months Ended	31 Months Ended
	Jun. 30, 2012	Jul. 09, 2012	Mar. 31, 2012	Jun. 30, 2012	Aug. 03, 2012 Stock Repurchase Plan	Aug. 03, 2012 Stock Repurchase Plan	Aug. 01, 2012 Dividend Declared [Member]
Subsequent Event [Line Items]
Total repurchase amount authorized		$ 500	$ 680
Acquisition of treasury stock (shares)	18,744,363			52,669,168	1,734,000	54,403,168
Treasury Stock Value Acquired Cost Method Excluding Commissions	$ 230			$ 608	$ 22	$ 630
Dividends Payable, Amount Per Share							$ 0.04
Treasury Stock Acquired Average Cost Per Share	$ 12.31			$ 11.57		$ 11.60