Income Taxes - Roll-forward of Unrecognized Tax Benefits and Associated Accrued Interest and Penalties (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Income Tax Contingency [Line Items]
Opening balance at January 1	$ 14.8
Increase for tax positions of prior periods	0.8
Decrease for settlement of tax positions	(4.6)
Closing balance at September 30	11.0
Current	0.0	$ (1.2)
Non-current	11.0	$ 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	0.8
Decrease for settlement of tax positions	(1.3)
Closing balance at September 30	3.8
Current	0.0
Non-current	3.8
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	(3.3)
Closing balance at September 30	7.2
Current	0.0
Non-current	$ 7.2