Investments (Details 6) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 88	$ 233	$ 236
Realized - impairments	(36)	(12)	(26)
Fixed maturities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	36	36	55
Realized - impairments	(15)	(5)	(9)
Change in unrealized	570	(945)	790
Equity securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	53	196	192
Realized - impairments	(26)	(5)	(24)
Change in unrealized	26	31	(23)
Mortgage Loans and Other Investments [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	1	2	(3)
Realized - impairments	0	(5)	0
Change in unrealized	0	0	0
Other, Including DPAC and Reserves on Annuity and Long-term Care [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(2)	(1)	(8)
Realized - impairments	5	3	7
Change in unrealized	(314)	504	(379)
Tax Effects [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(32)	(82)	(83)
Realized - impairments	13	4	9
Change in unrealized	(99)	144	(136)
Noncontrolling Interests [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(2)	(2)	(2)
Realized - impairments	1	0	0
Change in unrealized	(3)	6	(7)
Marketable Securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	54	149	151
Realized - impairments	(22)	(8)	(17)
Change in unrealized	$ 180	$ (260)	$ 245