Investments - Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		$ 306	$ (247)	$ 78
Realized - impairments		(19)	(19)	(73)
Total realized gains (losses) on securities		287	(266)	5
Net of tax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		242	(195)	51
Realized - impairments		(15)	(15)	(48)
Total realized gains (losses) on securities		227	(210)	3
Change in unrealized		779	(536)	436
Total pretax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		306	(247)	78
Realized - impairments		(19)	(19)	(73)
Total realized gains (losses) on securities		287	(266)	5
Change in unrealized		986	(679)	441
Fixed maturities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		26	6	17
Realized - impairments		(29)	(26)	(20)
Total realized gains (losses) on securities		(3)	(20)	(3)
Change in unrealized		1,821	(1,181)	532
Equity securities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		277	(265)	70
Realized - impairments		0	0	(64)
Total realized gains (losses) on securities		277	(265)	6
Change in unrealized		0	0	128
Mortgage loans and other investments
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		3	1	(6)
Realized - impairments		0	0	(4)
Total realized gains (losses) on securities		3	1	(10)
Change in unrealized		0	0	0
Other, Including DPAC and reserves on annuities and long-term care
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	[1]	0	11	(3)
Realized - impairments	[1]	10	7	15
Total realized gains (losses) on securities	[1]	10	18	12
Change in unrealized	[1]	(835)	502	(219)
Effects Of Tax Cuts And Jobs Act Of 2017
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments				0
Realized - impairments				0
Total realized gains (losses) on securities				0
Change in unrealized				149
Other tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments				(27)
Realized - impairments				25
Total realized gains (losses) on securities				(2)
Change in unrealized				(154)
Total tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(64)	52	(27)
Realized - impairments		4	4	25
Total realized gains (losses) on securities		(60)	56	(2)
Change in unrealized		$ (207)	$ 143	$ (5)

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