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Investments (held-to-maturity credit quality indicator) (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Dec. 31, 2020
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Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 10,550 | $ 11,697
Fixed Maturities Percent of Total Amortized cost | 100.00% | 100.00%
Standard & Poor's, AAA Rating [Member] |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 2,216 | $ 2,511
Fixed Maturities Percent of Total Amortized cost | 21.00% | 22.00%
Standard & Poor's, AA Rating [Member] |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 5,479 | $ 6,193
Fixed Maturities Percent of Total Amortized cost | 52.00% | 53.00%
Standard & Poor's, A Rating [Member] |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 2,011 | $ 2,138
Fixed Maturities Percent of Total Amortized cost | 19.00% | 18.00%
Standard & Poor's, BBB Rating [Member] |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 815 | $ 826
Fixed Maturities Percent of Total Amortized cost | 8.00% | 7.00%
Standard & Poor's, BB Rating [Member] |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 28 | $ 28
Fixed Maturities Percent of Total Amortized cost | 0.00% | 0.00%
Other [Member] |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 1 | $ 1
Fixed Maturities Percent of Total Amortized cost | 0.00% | 0.00%

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- Definition Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919253-210447 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953401-111524 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27232-111563 + Details
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