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Investments Investments (held-to-maturity credit quality indicator) (Details) - USD ($) $ in Millions | Mar. 31, 2021 | Dec. 31, 2020
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Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 11,175 | $ 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 | $ 2,404 | $ 2,511
Fixed Maturities Percent of Total Amortized cost | 22.00% | 22.00%
Standard & Poor's, AA Rating [Member] |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Debt Securities, Held-to-maturity | $ 5,815 | $ 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 | $ 2,109 | $ 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 | $ 818 | $ 826
Fixed Maturities Percent of Total Amortized cost | 7.00% | 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 of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562 Reference 2: 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=121645371&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details
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