Investments (Allowance on available-for-sale securities with credit impairments and PCD assets activity) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Allowance for credit losses:
Beginning balance	$ 0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	79
Available-for-sale securities accounted for as PCD assets	5
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	22
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	1
Write-offs charged against the allowance	0
Recoveries of amounts previously written off	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	(27)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	40
Impact of adopting ASC 326
Allowance for credit losses:
Beginning balance	6
Corporate and other bonds
Allowance for credit losses:
Beginning balance	0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	67
Available-for-sale securities accounted for as PCD assets	5
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	22
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	1
Write-offs charged against the allowance	0
Recoveries of amounts previously written off	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	(32)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	23
Corporate and other bonds | Impact of adopting ASC 326
Allowance for credit losses:
Beginning balance	6
Asset-backed
Allowance for credit losses:
Beginning balance	0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	12
Available-for-sale securities accounted for as PCD assets	0
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	0
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	0
Write-offs charged against the allowance	0
Recoveries of amounts previously written off	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	5
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	17
Asset-backed | Impact of adopting ASC 326
Allowance for credit losses:
Beginning balance	$ 0