Investments (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Net Investment Income [Line Items]
Gross investment income	$ 1,513	$ 1,363		$ 1,318
Investment expenses	(12)	(17)		(17)
Net investment income	1,501	1,346		1,301
Fixed maturities [Member]
Net Investment Income [Line Items]
Gross investment income	1,352	1,241		1,216
Equity securities [Member]
Net Investment Income [Line Items]
Gross investment income	66	50		36
Equity Method Investments [Member]
Net Investment Income [Line Items]
Gross investment income	18	0	[1]	0	[1]
Other [Member]
Net Investment Income [Line Items]
Gross investment income	$ 77	$ 72		$ 66

[1] Equity in the earnings of partnerships has not been material and was included in realized gains (losses) on securities prior to 2014.