Investments (Allowance on available-for-sale securities with credit impairments and assets purchased with credit deterioration) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Allowance for credit losses:
Balance beginning of period	$ 51	$ 0
Additions to the allowance for credit losses:
Balance beginning of period	51	0
For securities for which credit losses were not previously recorded	4	74
For available-for-sale securities accounted for as PCD assets	1	3
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	9	15
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	0	1
Write-offs charged against the allowance	0	0
Recoveries of amounts previously written off	0	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	0	(20)
Balance end of period	47	47
Corporate and other bonds
Allowance for credit losses:
Balance beginning of period	39	0
Additions to the allowance for credit losses:
Balance beginning of period	39	0
For securities for which credit losses were not previously recorded	4	62
For available-for-sale securities accounted for as PCD assets	1	3
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	9	15
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	0	1
Write-offs charged against the allowance	0	0
Recoveries of amounts previously written off	0	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	(1)	(21)
Balance end of period	34	34
Asset-backed
Allowance for credit losses:
Balance beginning of period	12	0
Additions to the allowance for credit losses:
Balance beginning of period	12	0
For securities for which credit losses were not previously recorded	0	12
For available-for-sale securities accounted for as PCD assets	0	0
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	0	0
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	0	0
Write-offs charged against the allowance	0	0
Recoveries of amounts previously written off	0	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	1	1
Balance end of period	$ 13	13
Impact of adopting ASC 326
Allowance for credit losses:
Balance beginning of period		6
Additions to the allowance for credit losses:
Balance beginning of period		6
Impact of adopting ASC 326 | Corporate and other bonds
Allowance for credit losses:
Balance beginning of period		6
Additions to the allowance for credit losses:
Balance beginning of period		6
Impact of adopting ASC 326 | Asset-backed
Allowance for credit losses:
Balance beginning of period		0
Additions to the allowance for credit losses:
Balance beginning of period		$ 0