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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) on securities	$ (2)	$ (2)	$ 12	$ (48)
Net of tax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) securities before impairments	(2)	(1)	11	(34)
Impairment allowance on securities	0	0	(2)	(4)
Realized gains (losses) on securities	(2)	(1)	9	(38)
Change in unrealized	(12)	(51)	(3)	33
Total pretax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) securities before impairments	(2)	(2)	14	(43)
Impairment allowance on securities	0	0	(2)	(5)
Realized gains (losses) on securities	(2)	(2)	12	(48)
Change in unrealized	(15)	(64)	(4)	43
Fixed maturities:
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) securities before impairments	(1)	(5)	(5)	(28)
Impairment allowance on fixed maturity securities	0	0	(2)	(5)
Realized gains (losses) on securities	(1)	(5)	(7)	(33)
Change in unrealized	(15)	(64)	(4)	43
Equity securities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) securities before impairments	(1)	3	19	(15)
Realized gains (losses) on securities	(1)	3	19	(15)
Change in unrealized	0	0	0	0
Mortgage loans and other investments
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) securities before impairments	0	0	0	0
Impairment allowance on mortgage loans and other investments	0	0	0	0
Realized gains (losses) on securities	0	0	0	0
Change in unrealized	0	0	0	0
Total tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) securities before impairments	0	1	(3)	9
Impairment allowance on securities	0	0	0	1
Realized gains (losses) on securities	0	1	(3)	10
Change in unrealized	$ 3	$ 13	$ 1	$ (10)