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Segments of Operations - Revenues by segment and sub-segment (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | $ 5,404 | $ 5,099 | $ 5,185
Net investment income | 730 | 461 | 532
Other income | 113 | 80 | 86
Revenues before realized gains (losses) | 6,438 | 5,821 | 6,058
Realized gains (losses) on securities | 110 | (75) | 155
Realized gains on subsidiaries | 4 | 23 | 0
Total revenues | 6,552 | 5,769 | 6,213
Real estate-related investments | Continuing operations |  |  |
Segment Reporting Information [Line Items] |  |  |
Net investment income | 51 | 49 | 37
Property and casualty insurance |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | 5,404 | 5,099 | 5,185
Net investment income | 663 | 399 | 472
Other income | 27 | 8 | 11
Revenues before realized gains (losses) | 6,094 | 5,506 | 5,668
Other |  |  |
Segment Reporting Information [Line Items] |  |  |
Revenues before realized gains (losses) | 293 | 266 | 353
Other | Real estate-related investments | Continuing operations |  |  |
Segment Reporting Information [Line Items] |  |  |
Net investment income | 51 | 49 | 37
Property and transportation | Property and casualty insurance |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | 2,144 | 1,871 | 1,828
Specialty casualty | Property and casualty insurance |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | 2,408 | 2,235 | 2,597
Specialty financial | Property and casualty insurance |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | 642 | 613 | 610
Other specialty | Property and casualty insurance |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | 210 | 180 | 150
Other lines | Property and casualty insurance |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | $ 0 | $ 200 | $ 0

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- Definition Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(2)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
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