Investments - Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		$ (9)	$ 36	$ 235	$ (25)
Realized — impairments		(9)	(2)	(13)	(3)
Realized gains (losses) on securities		(18)	34	222	(28)
Net of tax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(7)	28	186	(20)
Realized — impairments		(7)	(1)	(10)	(2)
Realized gains (losses) on securities		(14)	27	176	(22)
Change in unrealized		108	(98)	837	(526)
Total pretax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(9)	36	235	(25)
Realized — impairments		(9)	(2)	(13)	(3)
Realized gains (losses) on securities		(18)	34	222	(28)
Change in unrealized		137	(124)	1,060	(666)
Fixed maturities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		9	0	23	3
Realized — impairments		(14)	(2)	(20)	(3)
Realized gains (losses) on securities		(5)	(2)	3	0
Change in unrealized		367	(213)	2,009	(1,150)
Equity securities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(16)	33	210	(39)
Realized — impairments		0	0	0	0
Realized gains (losses) on securities		(16)	33	210	(39)
Change in unrealized		0	0	0	0
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	0	3	0
Realized — impairments		0	0	0	0
Realized gains (losses) on securities		0	0	3	0
Change in unrealized		0	0	0	0
Other, Including DPAC and reserves related to the annuity business
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	[1]	(2)	3	(1)	11
Realized — impairments	[1]	5	0	7	0
Realized gains (losses) on securities	[1]	3	3	6	11
Change in unrealized	[1]	(230)	89	(949)	484
Tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		2	(8)	(49)	5
Realized — impairments		2	1	3	1
Realized gains (losses) on securities		4	(7)	(46)	6
Change in unrealized		$ (29)	$ 26	$ (223)	$ 140

[1] Primarily adjustments to deferred policy acquisition costs and reserves related to the annuity business.