Investments (Details 6) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 106	$ 88	$ 233
Realized - impairments	(125)	(36)	(12)
Fixed maturities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	19	36	36
Realized - impairments	(43)	(15)	(5)
Change in unrealized	(941)	570	(945)
Equity securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	94	53	196
Realized - impairments	(94)	(26)	(5)
Change in unrealized	(134)	26	31
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	(2)	1	2
Realized - impairments	(3)	0	(5)
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	(5)	(2)	(1)
Realized - impairments	15	5	3
Change in unrealized	430	(314)	504
Total Pretax [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	106	88	233
Realized - impairments	(125)	(36)	(12)
Change in unrealized	(645)	282	(410)
Tax Effects [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(38)	(32)	(82)
Realized - impairments	45	13	4
Change in unrealized	226	(99)	144
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	2	1	0
Change in unrealized	8	(3)	6
Marketable Securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	66	54	149
Realized - impairments	(78)	(22)	(8)
Change in unrealized	$ (411)	$ 180	$ (260)