Supplementary Information of Average Historical Claims (Detail)	Dec. 31, 2024
Non-Core Operations \| Property Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Average annual percentage payout of incurred claims by age, net of reinsurance year one	76.40%
Average annual percentage payout of incurred claims by age, net of reinsurance year two	14.70%
Average annual percentage payout of incurred claims by age, net of reinsurance year three	2.40%
Average annual percentage payout of incurred claims by age, net of reinsurance year four	2.00%
Non-Core Operations \| Casualty Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Average annual percentage payout of incurred claims by age, net of reinsurance year one	8.10%
Average annual percentage payout of incurred claims by age, net of reinsurance year two	14.90%
Average annual percentage payout of incurred claims by age, net of reinsurance year three	17.30%
Average annual percentage payout of incurred claims by age, net of reinsurance year four	18.20%
Average annual percentage payout of incurred claims by age, net of reinsurance year five	8.30%
Average annual percentage payout of incurred claims by age, net of reinsurance year six	6.40%
Average annual percentage payout of incurred claims by age, net of reinsurance year seven	7.30%
Average annual percentage payout of incurred claims by age, net of reinsurance year eight	3.10%
Average annual percentage payout of incurred claims by age, net of reinsurance year nine	2.80%
Average annual percentage payout of incurred claims by age, net of reinsurance year ten	0.60%
Penn-America Segment \| Property Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Average annual percentage payout of incurred claims by age, net of reinsurance year one	64.50%
Average annual percentage payout of incurred claims by age, net of reinsurance year two	24.90%
Average annual percentage payout of incurred claims by age, net of reinsurance year three	2.10%
Penn-America Segment \| Casualty Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Average annual percentage payout of incurred claims by age, net of reinsurance year one	6.80%
Average annual percentage payout of incurred claims by age, net of reinsurance year two	14.70%
Average annual percentage payout of incurred claims by age, net of reinsurance year three	18.50%
Average annual percentage payout of incurred claims by age, net of reinsurance year four	20.90%
Average annual percentage payout of incurred claims by age, net of reinsurance year five	14.10%
Average annual percentage payout of incurred claims by age, net of reinsurance year six	10.60%
Average annual percentage payout of incurred claims by age, net of reinsurance year seven	5.60%
Average annual percentage payout of incurred claims by age, net of reinsurance year eight	2.10%
Average annual percentage payout of incurred claims by age, net of reinsurance year nine	1.80%
Average annual percentage payout of incurred claims by age, net of reinsurance year ten	1.40%

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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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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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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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