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Reinsurance (Components of Earned Premiums) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Premiums Earned, Net [Abstract] |  |  |
Direct | $ 12,997 | $ 12,001 | $ 11,491
Assumed | 288 | 288 | 338
Ceded | 5,110 | 4,640 | 4,401
Net | 8,175 | 7,649 | 7,428
Property and casualty |  |  |
Premiums Earned, Net [Abstract] |  |  |
Direct | 12,554 | 11,547 | 11,021
Assumed | 240 | 238 | 288
Ceded | 5,110 | 4,640 | 4,401
Net | 7,684 | 7,145 | 6,908
Long term care |  |  |
Premiums Earned, Net [Abstract] |  |  |
Direct | 443 | 454 | 470
Assumed | 48 | 50 | 50
Ceded | 0 | 0 | 0
Net | $ 491 | $ 504 | $ 520
Percentage of assumed premiums earned to net premiums earned |  |  |
Premiums Earned, Net [Abstract] |  |  |
Assumed/ Net % | 3.50% | 3.80% | 4.60%
Percentage of assumed premiums earned to net premiums earned | Property and casualty |  |  |
Premiums Earned, Net [Abstract] |  |  |
Assumed/ Net % | 3.10% | 3.30% | 4.20%
Percentage of assumed premiums earned to net premiums earned | Long term care |  |  |
Premiums Earned, Net [Abstract] |  |  |
Assumed/ Net % | 9.80% | 9.90% | 9.60%

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- Definition Amount of earned premiums assumed from other entities. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(1)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column D)) -URI http://asc.fasb.org/extlink&oid=120401096&loc=d3e574992-122915 + Details
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