Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (243.8)	$ (370.3)	$ (245.4)
Amounts reclassified from accumulated other comprehensive loss	16.3	7.8	3.2
Other comprehensive income (loss)	90.7	23.0	(22.5)
Ending Balance	(164.9)	(243.8)	(370.3)
Changes in Fair Value of Derivatives
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(11.0)	1.0
Other comprehensive income (loss) before reclassifications	(1.8)	(15.4)	1.1
Amounts reclassified from accumulated other comprehensive loss	11.9	3.4	(0.1)
Other comprehensive income (loss)	10.1	(12.0)	1.0
Ending Balance	(0.9)	(11.0)	1.0
Pension and OPEB Plan Cost
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(178.5)	(185.7)	(155.2)
Other comprehensive income (loss) before reclassifications	87.3	2.8	(29.7)
Amounts reclassified from accumulated other comprehensive loss	4.4	4.4	(0.8)
Other comprehensive income (loss)	91.7	7.2	(30.5)
Ending Balance	(86.8)	(178.5)	(185.7)
Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	35.6	8.5	1.4
Other comprehensive income (loss) before reclassifications	(11.0)	27.1	3.0
Amounts reclassified from accumulated other comprehensive loss			4.1
Other comprehensive income (loss)	(11.0)	27.1	7.1
Ending Balance	24.6	35.6	8.5
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(153.9)	(176.2)	(153.8)
Other comprehensive income (loss) before reclassifications	74.5	14.5	(25.6)
Amounts reclassified from accumulated other comprehensive loss	16.3	7.8	3.2
Other comprehensive income (loss)	90.8	22.3	(22.4)
Ending Balance	$ (63.1)	$ (153.9)	$ (176.2)