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v3.24.3

Concentration of Credit Risk - Additional Information (Details) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Sep. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) | Dec. 31, 2021 USD ($)
Concentration Risk [Line Items] |  |  |  |  |
Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments | $ 4,577.8 | $ 4,897.7 | $ 4,431.3 | $ 4,596.7 |
Concentration risk | 0.568 | 0.573 |  |  |
Reinsurance Recoverable, Allowance for Credit Loss | $ 3.7 | $ 3.7 | 11.5 |  | $ 3.3
Underwriting premiums receivables | 1,435.3 | 1,482.4 | 1,819.1 |  |
Due for settlement | 8.7 |  |  |  |
Underwriting premiums receivable, allowance for expected credit losses | $ 21.0 | $ 25.0 | $ 24.3 |  |
Allowable holdings of a single issue or issuer, percentage | 2.00% |  |  |  |
Maximum |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Gross written premiums, percentage | 15.90% | 16.30% |  |  |
Minimum |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Gross written premiums, percentage | 9.20% | 8.20% |  |  |
Median |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Gross written premiums, percentage | 11.10% | 9.70% |  |  |
A- rating or higher |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk | 0.429 | 0.423 |  |  |
A- rating or lower |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk | 0.003 | 0.004 |  |  |

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- Definition The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross premiums receivable to net realizable value. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(5)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-4 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 11B -Subparagraph (b) -SubTopic 10 -Topic 310 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-11B Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 + Details
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