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Segments of Operations - Narrative (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 USD ($) segment | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items] |  |  |
Number of segments | segment | 2 |  |
Percent of total revenue derived from sales of property and casualty insurance outside of the United States | 4.00% | 5.00% | 7.00%
Net earned premiums | $ 5,404 | $ 5,099 | $ 5,185
Net investment income | 730 | 461 | 532
Property and casualty insurance |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | 5,404 | 5,099 | 5,185
Net investment income | 663 | 399 | 472
Property and casualty insurance underwriting | 733 | 224 | 212
Investment and other income, net | 657 | 360 | 437
Property and casualty insurance | Other lines |  |  |
Segment Reporting Information [Line Items] |  |  |
Net earned premiums | 0 | 200 | 0
Property and casualty insurance underwriting | (4) | (202) | (113)
Special A&E charges |  | 47 | 18
Other |  |  |
Segment Reporting Information [Line Items] |  |  |
Loss on the retirement of debt |  | 5 | 5
Special charges to increase asbestos and environmental reserves |  | 21 | 11
Special A&E charges |  |  |
Segment Reporting Information [Line Items] |  |  |
Special A&E charges | $ 0 | 47 | 18
Special A&E charges | Property and casualty insurance | Other lines |  |  |
Segment Reporting Information [Line Items] |  |  |
Special A&E charges |  | 47 | $ 18
Neon Capital Limited |  |  |
Segment Reporting Information [Line Items] |  |  |
Net investment income |  | $ (5) |
Neon Capital Limited | Property and casualty insurance | Other lines |  |  |
Segment Reporting Information [Line Items] |  |  |
Percent of foreign sales attributable to Neon |  | 50.00% | 66.67%
Net earned premiums |  |  | $ 384
Net investment income |  | $ (5) |
Property and casualty insurance underwriting |  | (135) | (36)
Special charges related to the exit of certain lines of business within subsidiaries |  |  | $ 76
Investment and other income, net |  | $ (10) |

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