Investments - Allowance for credit losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance as of January 1, 2020	$ 14	$ 0
Credit losses on securities for which credit losses were not previously recorded	36	14
Initial allowance for credit losses recognized on financial assets accounted for as PCD	0	0
Reductions for securities sold during the period	0	0
Reductions for intent to sell or more likely than not will be required to sell securities prior to recovery of amortized cost	0	0
Increase (decrease) on securities with allowance recorded in previous period	(2)	0
Write-offs	0	0
Recoveries of amounts previously written off	0	0
Balance at December 31, 2020	48	14
Residential mortgage-backed securities
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance as of January 1, 2020	1	0
Credit losses on securities for which credit losses were not previously recorded	1	1
Initial allowance for credit losses recognized on financial assets accounted for as PCD	0	0
Reductions for securities sold during the period	0	0
Reductions for intent to sell or more likely than not will be required to sell securities prior to recovery of amortized cost	0	0
Increase (decrease) on securities with allowance recorded in previous period	(1)	0
Write-offs	0	0
Recoveries of amounts previously written off	0	0
Balance at December 31, 2020	1	1
Commercial mortgage-backed securities
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance as of January 1, 2020	0	0
Credit losses on securities for which credit losses were not previously recorded	0	0
Initial allowance for credit losses recognized on financial assets accounted for as PCD	0	0
Reductions for securities sold during the period	0	0
Reductions for intent to sell or more likely than not will be required to sell securities prior to recovery of amortized cost	0	0
Increase (decrease) on securities with allowance recorded in previous period	0	0
Write-offs	0	0
Recoveries of amounts previously written off	0	0
Balance at December 31, 2020	0	0
Foreign corporate private securities
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance as of January 1, 2020	11	0
Credit losses on securities for which credit losses were not previously recorded	35	11
Initial allowance for credit losses recognized on financial assets accounted for as PCD	0	0
Reductions for securities sold during the period	0	0
Reductions for intent to sell or more likely than not will be required to sell securities prior to recovery of amortized cost	0	0
Increase (decrease) on securities with allowance recorded in previous period	1	0
Write-offs	0	0
Recoveries of amounts previously written off	0	0
Balance at December 31, 2020	47	11
Other asset-backed securities
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance as of January 1, 2020	2	0
Credit losses on securities for which credit losses were not previously recorded	0	2
Initial allowance for credit losses recognized on financial assets accounted for as PCD	0	0
Reductions for securities sold during the period	0	0
Reductions for intent to sell or more likely than not will be required to sell securities prior to recovery of amortized cost	0	0
Increase (decrease) on securities with allowance recorded in previous period	(2)	0
Write-offs	0	0
Recoveries of amounts previously written off	0	0
Balance at December 31, 2020	$ 0	$ 2