Income Taxes - Components of Net Deferred Tax Asset (Liability) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Tax effect of temporary differences related to:
Inventories	$ 3.3	$ 4.2
Property and equipment	0.1
Accrued OPEB costs	3.0	3.7
Accrued pension costs	70.9	52.6
Currency revaluation on intercompany debt		24.0
Accrued environmental liabilities	28.8	41.1
Other deductible differences	11.7	25.5
Investments in subsidiaries and affiliates	2.7
Tax loss and tax credit carryforwards	116.2	142.6
Valuation allowance	(2.8)	(173.4)
Adjusted gross deferred tax assets	233.9	120.3
Netting of items by tax jurisdiction, assets	(114.1)	(120.3)
Net noncurrent deferred tax asset (liability)	119.8
Tax effect of temporary differences related to:
Inventories	(0.8)	(4.0)
Marketable securities	(25.4)	(59.9)
Property and equipment	(71.8)	(77.5)
Other taxable differences	(14.0)	(18.9)
Investments in subsidiaries and affiliates	(175.8)	(235.3)
Tax on unremitted earnings of non-U.S. subsidiaries	(9.5)	(2.8)
Adjusted gross deferred tax liabilities	(297.3)	(398.4)
Netting of items by tax jurisdiction, liabilities	(114.1)	(120.3)
Net noncurrent deferred tax asset (liability)	$ (183.2)	$ (278.1)