Investment Income and Gains and Losses - Write Downs and Sales (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Realized Gains (Losses) on Investments [Line Items]
Total		$ (59)	$ (10)	$ (85)	$ (26)
Sales Information For Available For Sale Fixed Maturities Equity Securities [Abstract]
Proceeds from sales		275	344	1,452	854
Gross gains on sales		31	13	82	38
Gross losses on sales		3	4	7	5
Debt Securities [Member]
Realized Gains (Losses) on Investments [Line Items]
Credit-related		(3)	0	(4)	0
Other	[1]	(55)	(9)	(69)	(10)
Total		(58)	(9)	(73)	(10)
Other [Member]
Realized Gains (Losses) on Investments [Line Items]
Credit-related	[2]	$ (1)	$ (1)	$ (12)	$ (16)

[1] Reflects other-than-temporary declines in fair values due to increases in market yields (widening of credit spreads) for certain below investment grade fixed maturities when there is an increased probability of sales activity prior to recovery of amortized cost.

[2] Other credit-related losses include other-than-temporary declines in fair values of equity securities, increases in valuation reserves on commercial mortgage loans and asset write-downs related to investments in real estate entities.