Investments - Rollforward of credit loss allowance for fixed income securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fixed income securities
Credit Losses on Fixed Income Securities
Beginning balance	$ (2)	$ (7)	$ (3)	$ 0
Credit losses on securities for which credit losses not previously reported	0	(1)	0	(10)
Net (increases) decreases related to credit losses previously reported	0	(1)	1	0
Reduction of allowance related to sales	0	1	0	2
Write-offs	0	0	0	0
Ending balance	(2)	(8)	(2)	(8)
Fixed income securities	2	8	2	8
Fixed income securities | Discontinued Operations, Held-for-sale
Credit Losses on Fixed Income Securities
Ending balance	(1)	(4)	(1)	(4)
Fixed income securities	1	4	1	4
Municipal
Credit Losses on Fixed Income Securities
Ending balance		(3)		(3)
Fixed income securities		3		3
Corporate
Credit Losses on Fixed Income Securities
Ending balance	(1)	(2)	(1)	(2)
Fixed income securities	1	2	1	2
ABS
Credit Losses on Fixed Income Securities
Ending balance	(1)	(2)	(1)	(2)
Fixed income securities	$ 1	2	$ 1	2
MBS
Credit Losses on Fixed Income Securities
Ending balance		(1)		(1)
Fixed income securities		$ 1		$ 1