Investments (Credit Loss Rollforward) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	$ 381	$ 391	$ 392	$ 471
Additions:
Initial impairments - credit loss OTTI recognized on securities not previously impaired	3	2	5	39
Additional impairments - credit loss OTTI recognized on securities previously impaired	23	15	64	41
Reductions:
Due to sales (maturities, pay downs or prepayments) during the period of securities previously credit loss OTTI impaired	(21)	(36)	(75)	(155)
Due to securities impaired to net present value of expected future cash flows	0	0	0	(23)
Increases in cash flows - accretion of previous credit loss OTTI	(1)	(1)	(1)	(2)
Balance, end of period	$ 385	$ 371	$ 385	$ 371