Pension - Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Loss (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Loss
Net loss (gain)	$ 2.6	$ 17.0	$ (4.8)
Pension Benefits
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Loss
Net loss (gain)	2.4	17.2	(4.7)
Prior service cost	0.0	0.0	0.4
Amortization of net loss	(1.5)	(0.5)	(0.7)
Amortization of prior service cost	0.1	(0.2)	(0.1)
Curtailments	(0.3)	1.0	0.0
Total recognized in other comprehensive income	0.7	17.5	(5.1)
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income	$ 2.9	$ 14.9	$ (12.1)

Other Comprehensive Income (Loss), Defined Benefit Plan, Curtailments Gain (Loss), Before Tax

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- Definition

Amount recognized in net periodic benefit cost (credit) and other comprehensive (income) loss.

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Amount, before tax, of cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive (income) loss for defined benefit plan, attributable to parent entity.

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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