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Income Taxes - Significant Portions of Deferred Tax Liabilities and Deferred Tax Assets (Detail) - USD ($) $ in Thousands | Dec. 31, 2025 | Dec. 31, 2024
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Schedule of Deferred Income Tax Assets and Liabilities [Line Items] |  |
Deferred Tax Assets, Net of Valuation Allowance | $ 6,583 | $ 15,108
Deferred tax assets: |  |
Net operating loss and capital carryforward | 356,575 | 349,931
OutsidDeferred Tax Assets Outside Basis Difference Discontinued Operationse basis difference |  | 17,044
Deferred Tax Asset, Interest Carryforward | 1,714 | 9,138
Deferred Tax Assets, Investments | 4,322 | 0
Loss reserves | 1,400 | 1,102
Deferred Tax Assets, Operating Loss Carryforwards, State and Local | 256,665 | 3,096
Deferred Tax Assets, Debentures | 12,813 | 0
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation | 189 | 1,423
Deferred Tax Assets, Variable Interest Entities | 1,721 | 0
Other | 1,262 | 429
Sub total deferred tax assets | 636,661 | 382,163
Valuation allowance | 630,078 | 367,055
Insurance intangible | 69,929 | 71,414
Unearned premiums and credit fees | 1,871 | 9,474
Investments | 0 | 3,568
Other | 0 | 787
Deferred Tax Liabilities, Gross | 71,800 | 85,243
Deferred Tax Liabilities, Net | 65,217 | 70,135
Deferred Income Tax Liabilities, Net | 65,217 | $ 70,135
Discontinued Operations |  |
Deferred tax assets: |  |
Deferred Income Tax Liabilities, Net | 20,382 |
Discontinued Operations, Held-for-Sale or Disposed of by Sale | Ambac Assurance Corporation |  |
Deferred tax assets: |  |
Other liabilities, net | $ 105,772 |

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