Investments (Net investment income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Investment Income [Line Items]
Gross investment income	$ 494	$ 568	$ 1,597	$ 1,719
Investment expense	(14)	(13)	(41)	(39)
Net investment income	480	555	1,556	1,680
Fixed maturity securities [Member]
Net Investment Income [Line Items]
Gross investment income	453	461	1,356	1,372
Short-term investments [Member]
Net Investment Income [Line Items]
Gross investment income	1	1	2	3
Limited partnership investments [Member]
Net Investment Income [Line Items]
Gross investment income	29	93	199	303
Total equity securities available-for-sale [Member]
Net Investment Income [Line Items]
Gross investment income	2	3	7	9
Mortgage loans [Member]
Net Investment Income [Line Items]
Gross investment income	7	6	22	17
Trading portfolio [Member]
Net Investment Income [Line Items]
Gross investment income	2	3	8	13
Other [Member]
Net Investment Income [Line Items]
Gross investment income		$ 1	$ 3	$ 2