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Investments - Available for sale fixed maturities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	$ 10,573		$ 10,752
Fixed maturities, available for sale, allowance for expected credit losses	10	$ 11	12	$ 16	$ 16	$ 11
Available for sale (AFS) fixed maturities	10,196		10,377
Total fixed maturities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	10,573		10,752
Fixed maturities, available for sale, allowance for expected credit losses	10		12
Fixed maturities, available for sale, gross unrealized, gains	86		107
Fixed maturities, available for sale, gross unrealized, losses	(453)		(470)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(367)		(363)
Available for sale (AFS) fixed maturities	10,196		10,377
U.S. government and government agencies
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	182		243
Fixed maturities, available for sale, allowance for expected credit losses	0		0
Fixed maturities, available for sale, gross unrealized, gains	0		1
Fixed maturities, available for sale, gross unrealized, losses	(6)		(8)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(6)		(7)
Available for sale (AFS) fixed maturities	176		236
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	917		1,014
Fixed maturities, available for sale, allowance for expected credit losses	0		0
Fixed maturities, available for sale, gross unrealized, gains	4		8
Fixed maturities, available for sale, gross unrealized, losses	(53)		(38)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(49)		(30)
Available for sale (AFS) fixed maturities	868		984
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	234		236
Fixed maturities, available for sale, allowance for expected credit losses	0		0
Fixed maturities, available for sale, gross unrealized, gains	1		1
Fixed maturities, available for sale, gross unrealized, losses	(4)		(7)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(3)		(6)
Available for sale (AFS) fixed maturities	231		230
Residential MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	1,805		1,788
Fixed maturities, available for sale, allowance for expected credit losses	1		1
Fixed maturities, available for sale, gross unrealized, gains	22		26
Fixed maturities, available for sale, gross unrealized, losses	(163)		(155)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(141)		(129)
Available for sale (AFS) fixed maturities	1,663		1,658
Commercial MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	70		75
Fixed maturities, available for sale, allowance for expected credit losses	0		0
Fixed maturities, available for sale, gross unrealized, gains	0		0
Fixed maturities, available for sale, gross unrealized, losses	0		(1)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	0		(1)
Available for sale (AFS) fixed maturities	70		74
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	1,467		1,709
Fixed maturities, available for sale, allowance for expected credit losses	3		3
Fixed maturities, available for sale, gross unrealized, gains	14		9
Fixed maturities, available for sale, gross unrealized, losses	(19)		(28)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(5)		(19)
Available for sale (AFS) fixed maturities	1,459		1,687
Other asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	2,450		2,477
Fixed maturities, available for sale, allowance for expected credit losses	6		5
Fixed maturities, available for sale, gross unrealized, gains	14		10
Fixed maturities, available for sale, gross unrealized, losses	(95)		(120)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(81)		(110)
Available for sale (AFS) fixed maturities	2,363		2,362
Corporate and other
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	3,448		3,210
Fixed maturities, available for sale, allowance for expected credit losses	0	$ 0	3	$ 5	$ 5	$ 1
Fixed maturities, available for sale, gross unrealized, gains	31		52
Fixed maturities, available for sale, gross unrealized, losses	(113)		(113)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(82)		(61)
Available for sale (AFS) fixed maturities	$ 3,366		$ 3,146