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		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		$ 58	$ 31	$ 244	$ (61)
Realized — impairments		(2)	0	(4)	(1)
Total realized gains (losses) on securities		56	31	240	(62)
Net of tax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		46	25	193	(48)
Realized — impairments		(1)	0	(3)	(1)
Total realized gains (losses) on securities		45	25	190	(49)
Change in unrealized		348	(151)	729	(428)
Total pretax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		58	31	244	(61)
Realized — impairments		(2)	0	(4)	(1)
Total realized gains (losses) on securities		56	31	240	(62)
Change in unrealized		440	(191)	923	(542)
Fixed maturities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		11	4	14	3
Realized — impairments		(3)	0	(6)	(1)
Total realized gains (losses) on securities		8	4	8	2
Change in unrealized		789	(338)	1,642	(937)
Equity securities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		44	23	226	(72)
Realized — impairments		0	0	0	0
Total realized gains (losses) on securities		44	23	226	(72)
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		3	0	3	0
Realized — impairments		0	0	0	0
Total realized gains (losses) on securities		3	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]	0	4	1	8
Realized — impairments	[1]	1	0	2	0
Total realized gains (losses) on securities	[1]	1	4	3	8
Change in unrealized	[1]	(349)	147	(719)	395
Tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(12)	(6)	(51)	13
Realized — impairments		1	0	1	0
Total realized gains (losses) on securities		(11)	(6)	(50)	13
Change in unrealized		$ (92)	$ 40	$ (194)	$ 114

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