Investments (Credit Loss Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	$ 280	$ 359	$ 357	$ 378
Additions:
Initial impairments — credit loss OTTI on securities not previously impaired	0	1	2	1
Additional impairments — credit loss OTTI on securities previously impaired	1	15	14	23
Reductions:
Sales (maturities, pay downs or prepayments) of securities previously impaired as credit loss OTTI	(22)	(11)	(113)	(31)
Securities impaired to net present value of expected future cash flows	0	0	0	(7)
Increase in cash flows — accretion of previous credit loss OTTI	(1)	0	(2)	0
Balance, end of period	$ 258	$ 364	$ 258	$ 364