Investments (Credit Loss Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	$ 357	$ 370	$ 357	$ 378
Additions:
Initial impairments — credit loss OTTI on securities not previously impaired	0	0	2	0
Additional impairments — credit loss OTTI on securities previously impaired	2	6	13	8
Reductions:
Sales (maturities, pay downs or prepayments) of securities previously impaired as credit loss OTTI	(78)	(10)	(91)	(20)
Securities impaired to net present value of expected future cash flows	0	(7)	0	(7)
Increase in cash flows — accretion of previous credit loss OTTI	(1)	0	(1)	0
Balance, end of period	$ 280	$ 359	$ 280	$ 359