Investments (Net investment income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Net Investment Income [Line Items]
Gross investment income	$ 539	$ 603
Investment expense	(13)	(12)
Net investment income	526	591
Fixed maturity securities [Member]
Net Investment Income [Line Items]
Gross investment income	452	457
Short term investments [Member]
Net Investment Income [Line Items]
Gross investment income	1	1
Limited partnership investments [Member]
Net Investment Income [Line Items]
Gross investment income	73	131
Equity securities [Member]
Net Investment Income [Line Items]
Gross investment income	2	3
Mortgage loans [Member]
Net Investment Income [Line Items]
Gross investment income	6	5
Trading portfolio [Member]
Net Investment Income [Line Items]
Gross investment income	3	5
Other [Member]
Net Investment Income [Line Items]
Gross investment income	$ 2	$ 1