Investments - Write Downs and Sales (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Realized Gains (Losses) on Investments [Line Items]
Total		$ (36)	$ (11)
Sales Information For Available For Sale Fixed Maturities Equity Securities [Abstract]
Proceeds from sales		361	393
Gross gains on sales		12	27
Gross losses on sales		5	2
Debt Securities [Member]
Realized Gains (Losses) on Investments [Line Items]
Credit-related		(18)	0
Non-credit related	[1]	(9)	(5)
Total		(27)	(5)
Other [Member]
Realized Gains (Losses) on Investments [Line Items]
Total	[2]	$ (9)	$ (6)

[1] These write-downs pertain to other-than-temporary declines in fair values due to increases in market yields (widening of credit spreads), particularly within the energy sector, for certain below investment grade fixed maturities with an increased probability of sales activity prior to recovery of amortized cost basis.

[2] Other asset write-downs include other-than-temporary declines in fair values of equity securities and asset write-downs related to real estate investments.