Investments (Details 6) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 19	$ 24	$ 71	$ 57
Realized — impairments	(35)	(11)	(69)	(13)
Fixed maturities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	7	10	17	32
Realized — impairments	(17)	(9)	(32)	(10)
Change in unrealized	(9)	(145)	(414)	466
Equity securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	13	16	59	26
Realized — impairments	(23)	(5)	(48)	(6)
Change in unrealized	(135)	(40)	(150)	3
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	0	(1)	(2)	0
Realized — impairments	0	0	0	0
Change in unrealized	0	0	0	0
Other [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(1)	(1)	(3)	(1)
Realized — impairments	5	3	11	3
Change in unrealized	(11)	60	166	(213)
Total Pretax [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	19	24	71	57
Realized — impairments	(35)	(11)	(69)	(13)
Change in unrealized	(155)	(125)	(398)	256
Tax Effects [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(7)	(10)	(25)	(21)
Realized — impairments	13	5	25	5
Change in unrealized	55	44	140	(90)
Noncontrolling Interests [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(1)	0	(1)	(1)
Realized — impairments	1	0	1	0
Change in unrealized	2	2	4	(3)
Marketable Securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	11	14	45	35
Realized — impairments	(21)	(6)	(43)	(8)
Change in unrealized	$ (98)	$ (79)	$ (254)	$ 163