Income Taxes - Details of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Stock compensation	$ 4.9	$ 4.3
Net operating loss carry forwards	8.8	15.9
Other intangible assets	5.6	4.8
Accretion expense	3.3	3.3
Restructuring provision	1.9	0.0
Other	4.8	4.5
Subtotal	29.3	32.8
Less valuation allowance	0.0	0.0
Total net deferred tax assets	29.3	32.8
Deferred tax liabilities:
Property, plant and equipment	(17.1)	(16.7)
Intangible assets including goodwill	(28.1)	(27.0)
Pension asset	(15.0)	(18.3)
Investment impairment recapture	(2.0)	(3.5)
Customer relationships	(4.9)	(5.8)
Unremitted overseas earnings	(1.1)	0.0
Other	(0.5)	0.0
Total deferred tax liabilities	(68.7)	(71.3)
Net deferred tax liability	(39.4)	(38.5)
Deferred tax assets	8.8	6.5
Deferred tax liabilities	(48.2)	(45.0)
Net deferred tax liability	$ (39.4)	$ (38.5)