Investments (Net investment income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Investment Income [Line Items]
Gross investment income	$ 2,506	$ 2,338	$ 2,112
Investment expense	(56)	(56)	(58)
Net investment income	2,450	2,282	2,054
Fixed maturity securities [Member]
Net Investment Income [Line Items]
Gross investment income	1,998	2,022	2,011
Short term investments [Member]
Net Investment Income [Line Items]
Gross investment income	3	5	8
Limited partnership investments [Member]
Net Investment Income [Line Items]
Gross investment income	451	251	48
Equity securities [Member]
Net Investment Income [Line Items]
Gross investment income	12	12	20
Mortgage loans [Member]
Net Investment Income [Line Items]
Gross investment income	23	17	9
Trading portfolio [Member]
Net Investment Income [Line Items]
Gross investment income	17	24	9
Other [Member]
Net Investment Income [Line Items]
Gross investment income	$ 2	$ 7	$ 7