Investments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
The credit portion of other-than-temporary impairments on fixed maturity securities, non-credit portion of an impairment has been recognized in other comprehensive income (loss)
Beginning Balance	$ 190	$ 151	$ 187	$ 143
Additional credit impairments on:
Previously impaired securities	1	22	4	29
Securities without prior impairments		4		5
Reductions-disposals		(6)		(6)
Ending Balance	$ 191	$ 171	$ 191	$ 171