Investments - Available for sale fixed maturities (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	$ 10,788	$ 10,687
Fixed maturities, available for sale, allowance for expected credit losses	41	34	$ 11	$ 12
Available for sale (AFS) fixed maturities	10,568	10,398
Total fixed maturities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	10,788	10,687
Fixed maturities, available for sale, allowance for expected credit losses	41	34
Fixed maturities, available for sale, gross unrealized, gains	122	98
Fixed maturities, available for sale, gross unrealized, losses	(301)	(353)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(179)	(255)
Available for sale (AFS) fixed maturities	10,568	10,398
U.S. government and government agencies
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	182	176
Fixed maturities, available for sale, allowance for expected credit losses	0	0
Fixed maturities, available for sale, gross unrealized, gains	1	0
Fixed maturities, available for sale, gross unrealized, losses	(3)	(3)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(2)	(3)
Available for sale (AFS) fixed maturities	180	173
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	921	905
Fixed maturities, available for sale, allowance for expected credit losses	0	0
Fixed maturities, available for sale, gross unrealized, gains	5	3
Fixed maturities, available for sale, gross unrealized, losses	(51)	(49)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(46)	(46)
Available for sale (AFS) fixed maturities	875	859
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	237	236
Fixed maturities, available for sale, allowance for expected credit losses	0	0
Fixed maturities, available for sale, gross unrealized, gains	4	2
Fixed maturities, available for sale, gross unrealized, losses	0	(1)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	4	1
Available for sale (AFS) fixed maturities	241	237
Residential MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	2,223	2,122
Fixed maturities, available for sale, allowance for expected credit losses	1	1
Fixed maturities, available for sale, gross unrealized, gains	29	22
Fixed maturities, available for sale, gross unrealized, losses	(133)	(154)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(104)	(132)
Available for sale (AFS) fixed maturities	2,118	1,989
Commercial MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	41	51
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	0
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	0	0
Available for sale (AFS) fixed maturities	41	51
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	1,250	1,243
Fixed maturities, available for sale, allowance for expected credit losses	4	4
Fixed maturities, available for sale, gross unrealized, gains	6	10
Fixed maturities, available for sale, gross unrealized, losses	(11)	(12)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(5)	(2)
Available for sale (AFS) fixed maturities	1,241	1,237
Other asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	2,420	2,412
Fixed maturities, available for sale, allowance for expected credit losses	6	6
Fixed maturities, available for sale, gross unrealized, gains	22	19
Fixed maturities, available for sale, gross unrealized, losses	(55)	(69)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	(33)	(50)
Available for sale (AFS) fixed maturities	2,381	2,356
Corporate and other
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	3,514	3,542
Fixed maturities, available for sale, allowance for expected credit losses	30	23	$ 0	$ 3
Fixed maturities, available for sale, gross unrealized, gains	55	42
Fixed maturities, available for sale, gross unrealized, losses	(48)	(65)
Fixed maturities, available-for-sale securities, accumulated gross unrealized gain (loss), before tax	7	(23)
Available for sale (AFS) fixed maturities	$ 3,491	$ 3,496