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Comprehensive Income - Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Income tax expense (benefit) | $ 1,241 | $ 867 | $ 4,030 | $ 767 |
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, after Tax | 522 | 142 | 1,108 | (214) |
Net of tax and noncontrolling interest | (112,620) | (27,503) | (231,710) | (8,183) |
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax | 79,520 | 133 | 93,763 | (9,669) |
Realized Investment Gains (Losses) | 507 | (577) | 507 | 3,959 |
Allowance for Credit Loss, Receivable, Other, Current | 238 |  | 238 |  | $ 238
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Net of tax and noncontrolling interest | (20,357) | (9) | (6,700) | (4,516) |
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax | (20,357) | (9) | (6,700) | (4,516) |
Realized Investment Gains (Losses) | (6,362) | 1,497 | 12,108 | (2,651) |
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, after Tax | (523) | (142) | (1,109) | 214 |
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax | 523 | 142 | 1,109 | (214) |
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, before Tax, after Reclassification Adjustment | (191) | 189 |  | (285) |
Accumulated Translation Adjustment [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax | 99,354 | 0 | 99,354 | 0 |
Accumulated Translation Adjustment [Member] | Discontinued Operations, Disposed of by Sale | Ambac Assurance Corporation [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Credit Risk Changes of Fair Value, Net Loss on Discontinued Operation | 698 |  | 698 |  |
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses) | 99,354 |  | 99,354 |  |
Realized Investment Gains (Losses) | (14,957) |  | (14,957) |  |
Reclassification out of Accumulated Other Comprehensive Income [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Net of tax and noncontrolling interest | 79,520 | 133 | 94,461 | (9,669) |
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Income tax expense (benefit) | (962) | 1,506 | 3,851 | 1,865 |
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Income tax expense (benefit) |  |  | 179 |  |
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Financial Liability, Fair Value Option, Including Portion Attributable to Noncontrolling Interest [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Income tax expense (benefit) | (16) | 47 |  | (71) |
Other Postretirement Benefits Plan [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax | 0 | 0 | 0 | (4,939) |
Other Postretirement Benefits Plan [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |
Income tax expense (benefit) | 0 | 0 | 0 | 0 |
Prior service cost | 0 | 0 | 0 | 0 |
Actuarial gains (losses) | 0 | 0 | 0 | 0 |
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax |  | 0 |  | 4,939 |
Total before tax | 0 | 0 | 0 | (4,939) |
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax | $ 0 | $ 0 | $ 0 | $ (4,939) |

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