Income Taxes - Schedule of Significant Deferred Tax Assets And Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Components Of Deferred Tax Assets And Liabilities [Abstract]
Pension and OPEB plan liabilities	$ 38.9	$ 43.9
Net operating losses and other tax carryforwards	255.2	280.0
Accrued liabilities	53.9	48.7
Foreign depreciation	30.6	36.4
Operating lease liabilities	48.7	0.0
Other	9.4	9.8
Total deferred tax assets	436.7	418.8
Valuation allowances	(237.5)	(255.9)
Net deferred tax assets	199.2	162.9
Accelerated depreciation	(70.3)	(64.3)
Other intangible assets	(9.4)	(11.8)
Inventories	(10.0)	(5.8)
Operating lease assets	(47.4)	0.0
Other	(16.4)	(18.9)
Total deferred tax liabilities	(153.5)	(100.8)
Net deferred tax assets	$ 45.7	$ 62.1