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Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
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Income Tax Disclosure [Abstract] |  |
Alternative minimum tax and other credit carryforwards | $ 768.9 | $ 867.3
Accrued and unfunded compensation and employee benefits | 431.5 | 364.4
Amortizable intangible assets | 94.7 | 122.9
Compensation expense related to stock options | 21.9 | 18.3
Accrued liabilities | 125.9 | 129.9
Investments | 1.9 | 1.2
Net operating loss carryforwards | 162.7 | 172.7
Capital loss carryforwards | 8.4 | 8.5
Other tax attributes | 1.9 | 34.7
Depreciable fixed assets | 22.0 | 13.2
Lease liabilities | 106.4 | 103.4
Capitalized indirect property costs | 0.2 | 0.2
Revenue recognition | 4.6 | 42.1
Other | 5.2 | 10.1
Total deferred tax assets | 1,756.2 | 1,888.9
Valuation allowance for deferred tax assets | (176.5) | (195.8)
Deferred tax assets | 1,579.7 | 1,693.1
Nondeductible amortizable intangible assets | 564.8 | 531.7
Accrued pension liability | 8.6 | 1.7
Investment-related partnerships | 4.2 | 6.5
Right-of-use assets | 97.1 | 95.0
Hedging instruments | 35.7 | 38.2
Other prepaid items | 16.4 | 17.4
Total deferred tax liabilities | 726.8 | 690.5
Net deferred tax assets | $ 852.9 | $ 1,002.6

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