Liabilities for Outstanding Claims, Losses and Loss Adjustment Expenses (Computation of Historical Claims on Paid and Incurred Claims Data, Net of Reinsurance) (Details)	Dec. 31, 2025
Core - Commercial Multiple Peril Line [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	33.40%
2	24.30%
3	9.90%
4	8.30%
5	7.80%
6	5.10%
7	4.40%
8	1.60%
Core - Workers' Compensation Line [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	22.10%
2	29.00%
3	15.20%
4	8.60%
5	4.80%
6	3.00%
7	2.80%
8	1.40%
9	1.10%
10	0.00%
Core - Commercial Automobile Line [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	12.80%
2	18.20%
3	19.70%
4	19.60%
5	12.80%
6	7.30%
7	2.50%
Core - General Liability And Umbrella - Occurrence [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	3.10%
2	9.20%
3	13.10%
4	16.30%
5	14.10%
6	9.30%
7	8.00%
8	9.40%
9	3.90%
10	3.70%
Specialty Property And Casualty [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	27.50%
2	21.40%
3	10.10%
4	11.30%
5	9.30%
6	5.80%
7	2.60%
8	1.70%
Specialty - General Liability - Claims Made [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	13.00%
2	25.90%
3	19.40%
4	12.60%
5	9.80%
6	4.50%
7	3.60%
Personal Automobile Lines [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	27.00%
2	29.50%
3	19.70%
4	12.30%
5	6.90%
Homeowners [Member]
Shortduration Insurance Contracts Historical Claims Duration [Line Items]
1	63.80%
2	27.80%
3	3.70%
4	1.70%

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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.

+ 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.

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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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