Investments (Details 25) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	$ 391	$ 401	$ 471	$ 443
Additions:
Initial impairments - credit loss OTTI recognized on securities not previously impaired	2	6	39	32
Additional impairments - credit loss OTTI recognized on securities previously impaired	15	39	41	79
Reductions:
Due to sales (maturities, pay downs or prepayments) during the period of securities previously credit loss OTTI impaired	(36)	(8)	(155)	(63)
Due to securities impaired to net present value of expected future cash flows	0	(1)	(23)	(45)
Due to increases in cash flows- accretion of previous credit loss OTTI	(1)	0	(2)	(9)
Balance, end of period	$ 371	$ 437	$ 371	$ 437