For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Data Type:	dtr-types:percentItemType
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Period Type:	duration

Commitments and Contingencies - Concentrations of credit risk (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Customer concentration risk \| Gross written premiums
Concentration Risk [Line Items]
Concentration risk, threshold	10.00%
Customer concentration risk \| Gross written premiums \| Marsh & McLennan Companies and its subsidiaries
Concentration Risk [Line Items]
Concentration risk percentage	19.00%	17.30%	18.30%
Customer concentration risk \| Gross written premiums \| AON Corporation and its subsidiaries
Concentration Risk [Line Items]
Concentration risk percentage	13.90%	13.80%	12.20%
Credit concentration risk \| Shareholders' equity
Concentration Risk [Line Items]
Concentration risk, threshold	10.00%