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Income Taxes - Roll-forward of Unrecognized Tax Benefits and Associated Accrued Interest and Penalties (Detail) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2024 | Dec. 31, 2023
Income Tax Contingency [Line Items] |  |
Opening balance at January 1 | $ 14.8 |
Increase for tax positions of prior periods | 0.5 |
Decrease for settlement of tax positions | (3.4) |
Closing balance at June 30 | 11.9 |
Current | (1.2) | $ (1.2)
Non-current | 10.7 | $ 13.6
Interest and Penalties [Member] |  |
Income Tax Contingency [Line Items] |  |
Opening balance at January 1 | 4.3 |
Increase for tax positions of prior periods | 0.5 |
Decrease for settlement of tax positions | (1.1) |
Closing balance at June 30 | 3.7 |
Current | (0.2) |
Non-current | 3.5 |
Unrecognized Tax Benefits [Member] |  |
Income Tax Contingency [Line Items] |  |
Opening balance at January 1 | 10.5 |
Increase for tax positions of prior periods | 0.0 |
Decrease for settlement of tax positions | (2.3) |
Closing balance at June 30 | 8.2 |
Current | (1.0) |
Non-current | $ 7.2 |

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