Investments - Schedule of Components of Restricted Assets (Details) - Asset Pledged as Collateral - USD ($) $ in Millions |
Mar. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] | ||
| Restricted investments | $ 209.8 | $ 220.2 |
| Securities and cash on deposit for regulatory and other purposes | ||
| Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] | ||
| Restricted investments | 167.2 | 180.1 |
| Securities and cash pledged as collateral for letters of credit | ||
| Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] | ||
| Restricted investments | $ 42.6 | $ 40.1 |