Investments and Derivative Instruments (Other-than-Temporary Impairment Losses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Other-Than-Temporary Impairment Losses
Balance, beginning of period	$ (1,319)		$ (1,598)		$ (1,632)
Securities not previously impaired	(27)	[1]	(41)	[1]	(181)	[1]
Securities previously impaired	(15)	[1]	(47)	[1]	(122)	[1]
Securities that matured or were sold during the period	543		358		314
Securities due to an increase in expected cash flows	5		9		23
Balance, end of period	$ (813)		$ (1,319)		$ (1,598)

[1] These additions are included in the net OTTI losses recognized in earnings in the Consolidated Statements of Operations.