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Income Tax Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2019
Federal Income Tax Note |  |  |  |
Less Tax Attributable to Temporary Items Included Above | $ 0.0 | $ (21.2) | $ (42.4) |
Unrecognized Tax Benefits, Interest on Income Taxes Expense | 11.2 | 13.2 | 12.2 |
Unrecognized Tax Benefits, Interest on Income Taxes Accrued | 70.6 | 59.4 | 46.2 |
Operating Loss Carryforwards | 61.2 |  |  |
Valuation Allowance on Deferred Tax Assets | 11.5 | 12.1 |  |
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount | 0.6 | 1.1 |  |
Income Taxes Paid, Net | 93.7 | 376.0 | 446.0 |
Deferred Tax Assets, Tax Credit Carryforwards | 101.2 | 0.0 |  |
Income Tax Paid, Federal, after Refund Received | 78.2 | 377.0 | 402.3 |
Income Tax Paid, Foreign, after Refund Received | 17.1 | 8.4 | 36.7 |
Income Tax Paid, State and Local, after Refund Received | (1.6) | $ (9.4) | 7.0 |
Capital Loss Carryforward | 135.2 |  |  |
Tax Year 2017 |  |  |  |
Federal Income Tax Note |  |  |  |
Increases for Tax Positions Related to Prior Years |  |  |  | $ 261.1
State and Local Jurisdiction |  |  |  |
Federal Income Tax Note |  |  |  |
Operating Loss Carryforwards | 186.7 |  |  |
UNITED KINGDOM |  |  |  |
Federal Income Tax Note |  |  |  |
Income Tax Paid, Foreign, after Refund Received | $ 15.9 |  | $ 34.4 |

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- Definition Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
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