Income Taxes - Schedule of Significant Deferred Tax Assets And Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Components Of Deferred Tax Assets And Liabilities [Abstract]
Pension and OPEB plan liabilities	$ 29.1	$ 38.9
Net operating losses and other tax carryforwards	195.6	205.6
Interest limitation carryforward	21.4	49.6
Accrued liabilities	48.6	53.9
Foreign depreciation	19.4	30.6
Operating lease liabilities	59.4	48.7
Other	16.7	9.4
Total deferred tax assets	390.2	436.7
Valuation allowances	(195.7)	(237.5)
Net deferred tax assets	194.5	199.2
Accelerated depreciation	(50.0)	(70.3)
Other intangible assets	(8.1)	(9.4)
Inventories	(8.6)	(10.0)
Operating lease assets	(58.1)	(47.4)
Other	(5.7)	(16.4)
Total deferred tax liabilities	(130.5)	(153.5)
Total net deferred tax assets	$ 64.0	$ 45.7