Investments (Credit Loss Rollforward) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	$ 357	$ 378
Additions:
Initial impairments — credit loss OTTI on securities not previously impaired	2	0
Additional impairments — credit loss OTTI on securities previously impaired	11	2
Reductions:
Due to sales (maturities, pay downs or prepayments) during the period of securities previously credit loss OTTI impaired	(13)	(10)
Balance, end of period	$ 357	$ 370