Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		12 Months Ended
	Jul. 01, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		$ (370.3)	$ (245.4)	$ (202.9)
Amounts reclassified from accumulated other comprehensive loss		7.8	3.2	4.4
Other comprehensive income (loss)		23.0	(22.5)	(28.5)
Ending Balance		(243.8)	(370.3)	(245.4)
ASU 2018-02
Accumulated Other Comprehensive Income Loss [Line Items]
Impact of adopting ASU 2018-02	$ 22.0
Changes in Fair Value of Derivatives
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		1.0
Other comprehensive income (loss) before reclassifications		(15.4)	1.1
Amounts reclassified from accumulated other comprehensive loss		3.4	(0.1)
Other comprehensive income (loss)		(12.0)	1.0
Ending Balance		(11.0)	1.0
Pension and OPEB Plan Cost
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		(185.7)	(155.2)	(144.6)
Other comprehensive income (loss) before reclassifications		2.8	(29.7)	6.4
Amounts reclassified from accumulated other comprehensive loss		4.4	(0.8)	4.4
Impact of adopting ASU 2018-02				(22.0)
Other				0.6
Other comprehensive income (loss)		7.2	(30.5)	11.4
Ending Balance		(178.5)	(185.7)	(155.2)
Pension and OPEB Plan Cost | ASU 2018-02
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss)				(10.6)
Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		8.5	1.4	40.9
Other comprehensive income (loss) before reclassifications		27.1	3.0	(39.5)
Amounts reclassified from accumulated other comprehensive loss			4.1
Other comprehensive income (loss)		27.1	7.1
Ending Balance		35.6	8.5	1.4
Translation Adjustments | ASU 2018-02
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss)				(39.5)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		(176.2)	(153.8)	(103.7)
Other comprehensive income (loss) before reclassifications		14.5	(25.6)	(33.1)
Amounts reclassified from accumulated other comprehensive loss		7.8	3.2	4.4
Impact of adopting ASU 2018-02				(22.0)
Other				0.6
Other comprehensive income (loss)		22.3	(22.4)	(28.1)
Ending Balance		$ (153.9)	$ (176.2)	(153.8)
Accumulated Other Comprehensive Loss | ASU 2018-02
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss)				$ (50.1)