Investments - Available for sale fixed maturities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	$ 10,610		$ 10,736
Fixed maturities, available for sale, allowance for expected credit losses	20	$ 16	11	$ 9	$ 7	$ 9
Available for sale (AFS) fixed maturities	9,931		10,095
Total fixed maturities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	10,610		10,736
Fixed maturities, available for sale, allowance for expected credit losses	20		11
Fixed maturities, available for sale, gross unrealized, gains	32		39
Fixed maturities, available for sale, gross unrealized, losses	(691)		(669)
Available for sale (AFS) fixed maturities	9,931		10,095
Total fixed maturities | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(659)		(630)
U.S. government and government agencies
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	240		233
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	(11)		(14)
Available for sale (AFS) fixed maturities	229		219
U.S. government and government agencies | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(11)		(14)
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	986		1,234
Fixed maturities, available for sale, allowance for expected credit losses	0		0
Fixed maturities, available for sale, gross unrealized, gains	1		3
Fixed maturities, available for sale, gross unrealized, losses	(76)		(51)
Available for sale (AFS) fixed maturities	911		1,186
States, municipalities and political subdivisions | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(75)		(48)
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	228		240
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	(10)		(14)
Available for sale (AFS) fixed maturities	218		226
Foreign government | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(10)		(14)
Residential MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	1,816		1,757
Fixed maturities, available for sale, allowance for expected credit losses	3		2
Fixed maturities, available for sale, gross unrealized, gains	18		23
Fixed maturities, available for sale, gross unrealized, losses	(212)		(180)
Available for sale (AFS) fixed maturities	1,619		1,598
Residential MBS | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(194)		(157)
Commercial MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	78		88
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	(2)		(3)
Available for sale (AFS) fixed maturities	76		85
Commercial MBS | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(2)		(3)
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	1,756		1,988
Fixed maturities, available for sale, allowance for expected credit losses	2		1
Fixed maturities, available for sale, gross unrealized, gains	8		1
Fixed maturities, available for sale, gross unrealized, losses	(39)		(67)
Available for sale (AFS) fixed maturities	1,723		1,921
Collateralized loan obligations | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(31)		(66)
Other asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	2,443		2,435
Fixed maturities, available for sale, allowance for expected credit losses	7		7
Fixed maturities, available for sale, gross unrealized, gains	2		1
Fixed maturities, available for sale, gross unrealized, losses	(161)		(184)
Available for sale (AFS) fixed maturities	2,277		2,245
Other asset-backed securities | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(159)		(183)
Corporate and other
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	3,063		2,761
Fixed maturities, available for sale, allowance for expected credit losses	8	$ 5	1	$ 0	$ 0	$ 1
Fixed maturities, available for sale, gross unrealized, gains	3		11
Fixed maturities, available for sale, gross unrealized, losses	(180)		(156)
Available for sale (AFS) fixed maturities	2,878		2,615
Corporate and other | Debt Securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	$ (177)		$ (145)