Acquisitions and Dispositions (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Discontinued Operations in Consolidated Statements of Operations
Total revenues									$ 74	$ 484	$ 464
Total expenses									0	363	406
Income (loss) before provision for income tax									74	121	58
Provision for income tax expense (benefit)									26	33	20
Income (loss) from operations of discontinued operations, net of income tax									48	88	38
Gain (loss) on disposal of operations, net of income tax									0	(64)	6
Income (loss) from discontinued operations, net of income tax	$ 31	$ 0	$ 3	$ 14	$ 25	$ 8	$ 31	$ (40)	$ 48	$ 24	$ 44