Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets
Receivable allowances	$ 0.4	$ 0.8
Inventory and other assets	0.0	1.1
Postretirement and other employee benefits	19.0	14.8
Derivatives	0.1	0.0
Net operating loss and tax credit carryforwards	93.7	93.3
Capital loss carryforward	6.9	0.0
Investment in subsidiaries	0.0	5.6
Intangibles	45.7	60.0
Other	3.9	1.2
Deferred Tax Assets	169.7	176.8
Less: Valuation allowance	(157.4)	(172.1)
Net deferred income tax assets	12.3	4.7
Deferred Tax Liabilities
Net property, plant and equipment	(52.6)	(51.9)
Accruals and other liabilities	(0.6)	(0.2)
Investment in subsidiaries	(3.5)	0.0
Derivatives	0.0	(0.3)
Other	(0.1)	0.0
Net deferred income tax liabilities	(56.8)	(52.4)
Total net deferred income tax liabilities	$ (44.5)	$ (47.7)