Reserves for Losses and Loss Settlement Expenses - Historical Claims Duration (Details)	Dec. 31, 2024
Commercial other liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	7.60%
Year 2	14.70%
Year 3	14.80%
Year 4	15.70%
Year 5	11.20%
Year 6	8.40%
Year 7	6.40%
Year 8	5.90%
Year 9	4.70%
Year 10	2.40%
Commercial fire and allied
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	59.60%
Year 2	22.90%
Year 3	6.40%
Year 4	4.00%
Year 5	2.40%
Year 6	1.10%
Year 7	0.40%
Year 8	0.00%
Year 9	0.50%
Year 10	0.10%
Commercial automobile
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	36.00%
Year 2	21.00%
Year 3	16.90%
Year 4	12.40%
Year 5	7.70%
Year 6	3.10%
Year 7	1.70%
Year 8	0.60%
Year 9	0.20%
Year 10	0.00%
Commercial workers' compensation
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	32.90%
Year 2	31.40%
Year 3	14.50%
Year 4	7.90%
Year 5	4.00%
Year 6	2.40%
Year 7	1.60%
Year 8	1.00%
Year 9	0.80%
Year 10	0.30%
Personal
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	55.10%
Year 2	33.00%
Year 3	6.20%
Year 4	2.10%
Year 5	0.80%
Year 6	0.40%
Year 7	0.30%
Year 8	0.10%
Year 9	0.40%
Year 10	0.00%

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- Definition

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 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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