Investments (Allowance on avaiable-for-sale securities with credit impairments and assets purchased with credit deterioration) (Details)	3 Months Ended
	Mar. 31, 2020 USD ($)
Reductions to the allowance for credit losses:
Balance end of period	$ 49,000,000
Corporate and other bonds
Allowance for credit losses:
Balance beginning of period	0
Additions to the allowance for credit losses:
Balance beginning of period	0
For securities for which credit losses were not previously recorded	48,000,000
For available-for-sale securities accounted for as PCD assets	1,000,000
Reductions to the allowance for credit losses:
Securities sold during the period (realized)	5,000,000
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis	1,000,000
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	0
Balance end of period	$ 49,000,000