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Investments - Rollforward of credit loss allowance for bank loans (Details) - Bank loans $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Debt and Equity Securities, FV-NI [Line Items] |
Beginning balance | $ 0
Net increases related to credit losses | (28)
Reduction of allowance related to sales | 9
Write-offs | 5
Ending balance | (67)
Cumulative effect of change in accounting principle |
Debt and Equity Securities, FV-NI [Line Items] |
Beginning balance | $ (53)
Ending balance |

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- Definition Amount, after recovery, of writeoff of financing receivable, charged against allowance for credit loss. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 + Details
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