Investments - Allowance for credit losses on fixed maturities (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Jan. 01, 2020
Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 61	$ 0
Impact of adoption of new accounting policy	61	0
Initial allowance for purchased securities with credit deterioration	0	1
Provision for expected credit losses on securities with no previous allowance	0	67
Additions (reductions) to previously recognized expected credit losses	(3)	(10)
Reductions due to sales or redemptions	4	4
Ending balance	54	54
Structured securities
Allowance for Credit Losses [Roll Forward]
Beginning balance	39	0
Impact of adoption of new accounting policy	39	39	$ 0
Initial allowance for purchased securities with credit deterioration	0	1
Provision for expected credit losses on securities with no previous allowance	0	39
Additions (reductions) to previously recognized expected credit losses	1	0
Reductions due to sales or redemptions	1	1
Ending balance	39	39
Corporate and other
Allowance for Credit Losses [Roll Forward]
Beginning balance	22	0
Impact of adoption of new accounting policy	15	15	0
Initial allowance for purchased securities with credit deterioration	0	0
Provision for expected credit losses on securities with no previous allowance	0	28
Additions (reductions) to previously recognized expected credit losses	(4)	(10)
Reductions due to sales or redemptions	3	3
Ending balance	$ 15	$ 15
Accounting Standards Update 2016-13
Allowance for Credit Losses [Roll Forward]
Impact of adoption of new accounting policy			$ 0