Liability for Losses and Loss Expenses - Supplementary Information about Average Historical Claims Duration (Details)	Dec. 31, 2025
Personal Automobile [Member]
Liability for Losses and Loss Expenses [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	65.70%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	17.40%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	9.10%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	4.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	2.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	0.80%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	0.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 8	0.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 9	0.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.00%
Homeowners [Member]
Liability for Losses and Loss Expenses [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	80.70%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	16.30%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	1.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	0.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	0.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	0.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	0.10%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 8	0.10%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 9	0.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.10%
Commercial Automobile [Member]
Liability for Losses and Loss Expenses [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	41.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	18.30%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	14.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	11.90%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	7.60%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	3.80%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	1.70%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 8	0.40%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 9	0.60%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.00%
Commercial Multi-Peril [Member]
Liability for Losses and Loss Expenses [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	42.80%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	18.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	9.90%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	10.40%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	7.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	4.70%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	2.60%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 8	1.80%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 9	0.30%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.00%
Workers' Compensation [Member]
Liability for Losses and Loss Expenses [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	30.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	32.40%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	15.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	8.30%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	3.40%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	2.30%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	1.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 8	0.90%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 9	0.60%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.70%

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.

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

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

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4D
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-4D

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

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-4B

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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.

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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.

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- Definition

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.

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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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- Definition

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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