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Reinsurance (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Percentage of ceded earned premiums to gross earned premiums | 38.00% | 35.00% | 37.00% | 37.00%
Percentage of assumed earned premiums to net earned premiums | 29.00% | 24.00% | 26.00% | 25.00%
Underwriting [Member] |  |  |  |
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Gross losses and loss adjustment expenses | $ 1,476,189 | $ 1,186,691 | $ 2,868,537 | $ 2,337,040
Ceded losses | 288,676 | 127,895 | 507,931 | 305,889
Program services and other fronting [Member] |  |  |  |
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Gross losses and loss adjustment expenses | 594,700 | 574,800 | 1,100,000 | 990,500
Ceded losses | $ (594,300) | $ (574,800) | $ (1,091,000) | $ (990,500)

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