Valuation and Qualifying Accounts (Details) (Valuation Allowance of Deferred Tax Assets [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Valuation Allowance of Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at January 1	$ 1,626	$ 977	$ 435	$ 437
Additions to deferred income tax expense	762	723	22
Reductions of deferred income tax expense	(103)	(149)	(24)
Valuation release to equity	(10)	(32)	0
Balance at December 31	$ 1,626	$ 977	$ 435	$ 437