Investments (Net investment income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Investment Income [Line Items]
Gross investment income	$ 564	$ 548	$ 1,103	$ 1,151
Investment expense	(14)	(14)	(27)	(26)
Net investment income	550	534	1,076	1,125
Fixed maturity securities [Member]
Net Investment Income [Line Items]
Gross investment income	451	454	903	911
Short-term investments [Member]
Net Investment Income [Line Items]
Gross investment income		1	1	2
Limited partnership investments [Member]
Net Investment Income [Line Items]
Gross investment income	97	79	170	210
Total equity securities available-for-sale [Member]
Net Investment Income [Line Items]
Gross investment income	3	3	5	6
Mortgage loans [Member]
Net Investment Income [Line Items]
Gross investment income	9	6	15	11
Trading portfolio [Member]
Net Investment Income [Line Items]
Gross investment income	3	5	6	10
Other [Member]
Net Investment Income [Line Items]
Gross investment income	$ 1		$ 3	$ 1