Income Taxes - Components of Net Deferred Tax Asset (Liability) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Tax effect of temporary differences related to:
Inventories	$ 4.7	$ 3.3
Property and equipment		0.1
Accrued OPEB costs	2.8	3.0
Accrued pension costs	75.5	70.9
Accrued environmental liabilities	35.8	28.8
Other deductible differences	10.3	11.7
Investments in subsidiaries and affiliates	2.6	2.7
Tax loss and tax credit carryforwards	93.9	116.2
Valuation allowance	(10.0)	(2.8)
Adjusted gross deferred tax assets	215.6	233.9
Netting of items by tax jurisdiction, assets	(114.6)	(114.1)
Net noncurrent deferred tax asset (liability)	101.0	119.8
Tax effect of temporary differences related to:
Inventories	(3.3)	(0.8)
Marketable securities	(0.2)	(25.4)
Property and equipment	(69.0)	(71.8)
Other taxable differences	(13.2)	(14.0)
Investments in subsidiaries and affiliates	(58.8)	(175.8)
Tax on unremitted earnings of non-U.S. subsidiaries	(11.3)	(9.5)
Adjusted gross deferred tax liabilities	(155.8)	(297.3)
Netting of items by tax jurisdiction, liabilities	(114.6)	(114.1)
Net noncurrent deferred tax asset (liability)	$ (41.2)	$ (183.2)