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Derivative Contracts - Additional Information (Details) - USD ($) $ in Millions |  | 12 Months Ended
--- | --- | ---
Oct. 01, 2022 | Dec. 31, 2024 | Dec. 31, 2023
Reinsurance Contracts [Axis]: Funds withheld credited with interest for periods after October 1, 2022 |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Reinsurance Retention Policy, Retrocession Premium, Interest Rate | 1.75% |  |
Level 3 | Liability | Fair Value, Recurring [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Liability, increase (decrease) in fv included in net income |  | $ 12.9 | $ 15.2
Foreign exchange contracts | Not Designated as Hedging Instrument |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Purchase of US and foreign exchange |  | 1,586.9 | 1,802.9
Gain (loss) to net income from derivative instruments |  | (34.0) | 10.9
Foreign exchange contracts | Not Designated as Hedging Instrument | Derivative liabilities |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Purchase of US and foreign exchange |  | 1,036.9 | 540.8
Foreign exchange contracts | Designated as Hedging Instrument | Derivative liabilities |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Purchase of US and foreign exchange |  | 158.0 | 0.0
Foreign exchange contracts | Net change from current period hedged transactions | Designated as Hedging Instrument |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (loss) on foreign currency fair value hedge derivatives |  | (6.5) | (14.0)
Foreign exchange contracts | General, administrative and corporate expenses | Designated as Hedging Instrument |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (loss) on foreign currency fair value hedge derivatives |  | (0.9) | (8.1)
Foreign exchange contracts | General, administrative and corporate expenses | Designated as Hedging Instrument | Forecast |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (loss) on foreign currency fair value hedge derivatives |  | (6.2) |
Loss Portfolio Transfer | Level 3 | Liability | Fair Value, Recurring [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Liability, increase (decrease) in fv included in net income |  | $ 12.9 | $ 15.2

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4E -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4E + Details
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