Investments (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
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	$ 191	$ 171	$ 187	$ 143
Additional credit impairments on:
Previously impaired securities		8	4	37
Securities without prior impairments		2		7
Reductions-disposals		(1)		(7)
Ending Balance	$ 191	$ 180	$ 191	$ 180