Investments (Allowance on available-for-sale securities with credit impairments and PCD assets activity) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Allowance for credit losses:
Balance at beginning of period	$ 40	$ 0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	14	48
Available-for-sale securities accounted for as PCD assets	2	1
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	6	5
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	(7)	0
Balance at end of period	43	49
Impact of adopting ASC 326
Allowance for credit losses:
Balance at beginning of period		6
Corporate and other bonds
Allowance for credit losses:
Balance at beginning of period	23	0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	14	48
Available-for-sale securities accounted for as PCD assets	2	1
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	6	5
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	(6)	0
Balance at end of period	27	49
Corporate and other bonds | Impact of adopting ASC 326
Allowance for credit losses:
Balance at beginning of period		6
Asset-backed
Allowance for credit losses:
Balance at beginning of period	17	0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	0	0
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)	0
Balance at end of period	$ 16	0
Asset-backed | Impact of adopting ASC 326
Allowance for credit losses:
Balance at beginning of period		$ 0