Reserve for Losses and Loss Adjustment Expenses - Schedule of Average Annual Percentage Payouts of Incurred Claims by Age, Net of Reinsurance (Details)	Dec. 31, 2025
E&S – excluding commercial auto \| Excess and Surplus Lines
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	3.20%
Year 2	11.10%
Year 3	14.50%
Year 4	16.20%
Year 5	14.30%
Year 6	11.90%
Year 7	9.50%
Year 8	8.00%
Year 9	5.20%
Year 10	5.10%
Commercial Auto \| Excess and Surplus Lines
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	9.00%
Year 2	14.70%
Year 3	21.80%
Year 4	20.20%
Year 5	16.20%
Year 6	8.10%
Year 7	3.60%
Year 8	1.60%
Year 9	1.20%
Year 10	0.40%
Individual Risk Workers' Compensation \| Specialty Admitted Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	29.10%
Year 2	33.20%
Year 3	14.70%
Year 4	7.90%
Year 5	6.10%
Year 6	3.10%
Year 7	2.00%
Year 8	0.90%
Year 9	1.00%
Year 10	0.70%
Fronting and Programs \| Specialty Admitted Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	20.20%
Year 2	21.80%
Year 3	19.30%
Year 4	13.30%
Year 5	7.90%
Year 6	5.20%
Year 7	3.30%
Year 8	2.90%
Year 9	3.30%
Year 10	1.50%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage of average annual payout, after reinsurance, in the eighth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 9F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-9F

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4G
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-4G

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Percentage of average annual payout, after reinsurance, in the fifth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

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Percentage of average annual payout, after reinsurance, in the fourth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

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Percentage of average annual payout, after reinsurance, in the ninth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

+ References

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Percentage of average annual payout, after reinsurance, in the first year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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Percentage of average annual payout, after reinsurance, in the seventh year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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Percentage of average annual payout, after reinsurance, in the sixth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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Percentage of average annual payout, after reinsurance, in the tenth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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Percentage of average annual payout, after reinsurance, in the third year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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Percentage of average annual payout, after reinsurance, in the second year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts.

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