Liability for Losses and Loss Expenses, Supplementary Information About Average Historical Claims Duration (Details)	Dec. 31, 2021
Personal Automobile [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	64.80%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	16.90%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	8.60%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	4.30%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	2.30%
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	0.40%
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	0.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.00%
Homeowners [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	81.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	15.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	1.30%
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	0.30%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	0.10%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	0.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 8	0.00%
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%
Commercial Automobile [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	41.70%
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	12.80%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	12.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	6.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	3.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	1.10%
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	0.80%
Commercial Multi-Peril [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	45.40%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	16.90%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 3	9.40%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 4	10.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	6.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	3.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 7	1.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 8	0.60%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 9	0.20%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.40%
Workers Compensation [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Abstract]
Average annual percentage payout of incurred claims by age, net of reinsurance, year 1	31.00%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 2	31.80%
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	7.70%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 5	3.70%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 6	1.90%
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	0.70%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 9	0.50%
Average annual percentage payout of incurred claims by age, net of reinsurance, year 10	0.80%

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4G
-URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671329-158438

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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.

+ 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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- Definition

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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