Plant Closures and Divestitures - Summary of Restructuring Activities and Related Reserves (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	$ 4.0	$ 8.1
Accrual	4.2	6.4
Cost charged against assets	(0.8)	(3.0)
Reversal of accrued charges	(0.3)	(0.4)
Cash paid		(7.0)
Currency translation		(0.1)
Reserve, Ending Balance	7.1	4.0
Severance and Employee Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	0.9	1.7
Accrual	0.5	0.0
Cost charged against assets	(0.0)	(0.0)
Reversal of accrued charges	(0.3)	(0.3)
Cash paid		(0.5)
Currency translation		0.0
Reserve, Ending Balance	1.1	0.9
Asset Retirement [Member]
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	0.7	3.6
Accrual	2.9	3.4
Cost charged against assets	(0.0)	(0.0)
Reversal of accrued charges	(0.0)	(0.1)
Cash paid		(6.2)
Currency translation		0.0
Reserve, Ending Balance	3.6	0.7
Other [Member]
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	2.4	2.8
Accrual	0.8	3.0
Cost charged against assets	(0.8)	(3.0)
Reversal of accrued charges	(0.0)	(0.0)
Cash paid		(0.3)
Currency translation		(0.1)
Reserve, Ending Balance	$ 2.4	$ 2.4