Investments (Allowance on available-for-sale securities with credit impairments and PCD assets activity) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allowance for credit losses:
Balance at beginning of period	$ 45	$ 51	$ 40	$ 0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	0	4	14	74
Available-for-sale securities accounted for as PCD assets	2	1	8	3
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	0	9	6	15
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	0	0	0	1
Write-offs charged against the allowance	16	0	16	0
Recoveries of amounts previously written off	0	0	0	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	0	0	(9)	(20)
Balance at end of period	31	47	31	47
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	24	39	23	0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	0	4	14	62
Available-for-sale securities accounted for as PCD assets	2	1	4	3
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	0	9	6	15
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	0	0	0	1
Write-offs charged against the allowance	16	0	16	0
Recoveries of amounts previously written off	0	0	0	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	0	(1)	(9)	(21)
Balance at end of period	10	34	10	34
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	21	12	17	0
Additions to the allowance for credit losses:
Securities for which credit losses were not previously recorded	0	0	0	12
Available-for-sale securities accounted for as PCD assets	0	0	4	0
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	0	0	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	0	0
Write-offs charged against the allowance	0	0	0	0
Recoveries of amounts previously written off	0	0	0	0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period	0	1	0	1
Balance at end of period	$ 21	$ 13	$ 21	13
Asset-backed | Impact of adopting ASC 326
Allowance for credit losses:
Balance at beginning of period				$ 0