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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

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- Definition Amount of expense for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), for which no credit loss was previously recorded. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455 + Details
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