Investments and Derivative Instruments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013	Mar. 31, 2012
Other-Than-Temporary Impairment Losses
Balance as of beginning of period					$ (813)	$ (1,319)	$ (699)	$ (1,158)
Additions for credit impairments recognized on securities not previously impaired	0	[1]	(4)	[1]	(8)	(21)
Additions for credit impairments recognized on securities previously impaired	(3)	[1]	(7)	[1]	(3)	(15)
Securities that matured or were sold during the period	34		96		152	279
Securities Intends to Sell or More Likely Than Not Will Be Required to Sell Before Recovery	2		0		2	0
Securities due to an increase in expected cash flows	7		1		11	4
Balance as of end of period	$ (659)		$ (1,072)		$ (659)	$ (1,072)	$ (699)	$ (1,158)

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