Municipal Bond Guarantee Reinsurance - Schedule of Change in the Fair Value of BAM Surplus Notes (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Dec. 31, 2025 |
|
| Changes In Nominal Value Of Surplus Notes [Roll Forward] | |||||
| Interest income from BAM Surplus Notes | $ 6.9 | $ 7.5 | $ 13.8 | $ 15.0 | |
| Operating Segments | HG Global | |||||
| Changes In Nominal Value Of Surplus Notes [Roll Forward] | |||||
| Beginning nominal value | 497.4 | 503.2 | 490.5 | 495.7 | |
| Interest income from BAM Surplus Notes | 6.9 | 7.5 | 13.8 | 15.0 | |
| Payments of principal and interest | 0.0 | 0.0 | 0.0 | 0.0 | |
| Ending nominal value | 504.3 | 510.7 | 504.3 | 510.7 | |
| Changes In Fair Value Discount Of Surplus Notes [Roll Forward] | |||||
| Beginning fair value discount | (151.5) | (114.0) | (151.5) | (114.0) | |
| Change in fair value of BAM Surplus Notes | 0.0 | 0.0 | 0.0 | 0.0 | |
| Ending fair value discount | (151.5) | (114.0) | (151.5) | (114.0) | |
| BAM Surplus Notes, at fair value | $ 352.8 | $ 396.7 | $ 352.8 | $ 396.7 | $ 339.0 |