Income Taxes - Schedule of Significant Deferred Tax Assets And Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Components Of Deferred Tax Assets And Liabilities [Abstract]
Pension and OPEB plan liabilities	$ 43.9	$ 58.8
Net operating losses and other tax carryforwards	280.0	255.1
Accrued liabilities	48.7	51.5
Foreign depreciation	36.4	19.4
Other	9.8	16.5
Total deferred tax assets	418.8	401.3
Valuation allowances	(255.9)	(238.3)
Net deferred tax assets	162.9	163.0
Accelerated depreciation	(64.3)	(45.8)
Other intangible assets	(11.8)	(20.0)
Inventories	(5.8)	(7.3)
Other	(18.9)	(14.0)
Total deferred tax liabilities	(100.8)	(87.1)
Net deferred tax assets	$ 62.1	$ 75.9