Investments and Derivative Instruments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Mar. 31, 2012	Mar. 31, 2011
Other-Than-Temporary Impairment Losses
Balance as of beginning of period					$ (1,319)		$ (1,598)		$ 1,158	$ (1,510)
Additions for credit impairments recognized on securities not previously impaired	(4)	[1]	(3)	[1]	(21)	[1]	(26)	[1]
Additions for credit impairments recognized on securities previously impaired	(7)	[1]	(26)	[1]	(15)	[1]	(42)	[1]
Securities that matured or were sold during the period	96		121		279		243
Securities due to an increase in expected cash flows	1		1		4		6
Balance as of end of period	$ 1,072		$ (1,417)		$ 1,072		$ (1,417)		$ 1,158	$ (1,510)

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