Short Duration Contracts - Percentage annual payout - all segments (Details)	Dec. 31, 2024
Insurance \| Property, energy, marine and aviation
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	21.50%
Year Two	43.80%
Year Three	17.20%
Year Four	6.10%
Year Five	2.40%
Year Six	0.00%
Year Seven	0.00%
Year Eight	0.30%
Year Nine	(1.20%)
Year Ten	0.00%
Insurance \| Third party occurrence business
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	3.60%
Year Two	10.00%
Year Three	12.30%
Year Four	13.20%
Year Five	10.00%
Year Six	10.00%
Year Seven	5.50%
Year Eight	5.50%
Year Nine	4.80%
Year Ten	2.20%
Insurance \| Third party claims-made business
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	4.40%
Year Two	15.60%
Year Three	16.30%
Year Four	10.90%
Year Five	14.30%
Year Six	10.90%
Year Seven	7.00%
Year Eight	6.20%
Year Nine	4.00%
Year Ten	2.40%
Insurance \| Multi-line and other specialty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	32.80%
Year Two	29.20%
Year Three	11.00%
Year Four	8.50%
Year Five	5.10%
Year Six	3.30%
Year Seven	1.70%
Year Eight	1.10%
Year Nine	0.80%
Year Ten	1.40%
Reinsurance \| Casualty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	2.80%
Year Two	8.30%
Year Three	11.90%
Year Four	11.90%
Year Five	11.50%
Year Six	8.40%
Year Seven	7.50%
Year Eight	7.20%
Year Nine	6.00%
Year Ten	3.40%
Reinsurance \| Property catastrophe
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	(134.20%)
Year Two	168.40%
Year Three	(22.50%)
Year Four	213.90%
Year Five	(38.40%)
Year Six	9.10%
Year Seven	(12.10%)
Year Eight	1.50%
Year Nine	(0.80%)
Year Ten	9.40%
Reinsurance \| Property excluding property catastrophe
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	23.60%
Year Two	36.20%
Year Three	14.70%
Year Four	6.80%
Year Five	4.70%
Year Six	0.20%
Year Seven	0.80%
Year Eight	0.20%
Year Nine	1.10%
Year Ten	0.10%
Reinsurance \| Marine and aviation
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	1.40%
Year Two	28.90%
Year Three	20.30%
Year Four	13.80%
Year Five	10.00%
Year Six	4.90%
Year Seven	2.30%
Year Eight	1.40%
Year Nine	0.60%
Year Ten	0.40%
Reinsurance \| Other specialty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	27.70%
Year Two	29.20%
Year Three	14.20%
Year Four	6.40%
Year Five	5.20%
Year Six	4.00%
Year Seven	1.60%
Year Eight	0.70%
Year Nine	0.30%
Year Ten	0.30%
Mortgage
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year One	4.50%
Year Two	26.10%
Year Three	23.70%
Year Four	11.40%
Year Five	7.20%
Year Six	2.50%
Year Seven	1.50%
Year Eight	1.00%
Year Nine	0.50%
Year Ten	0.50%

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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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- Definition

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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- 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.

+ References

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- Definition

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.

+ References

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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.

+ References

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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.

+ References

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- Definition

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.

+ References

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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.

+ References

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