Income Taxes (Significant Components of the Company's Net Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred income tax assets:
Postretirement benefit obligation	$ 1.7	$ 1.7
Inventory	0.8	8.7
Net operating loss and credit carryforwards	16.4	11.6
Operating lease liabilities	15.4	13.8
Compensation	3.9	2.9
Disallowed interest	0.0	4.6
Other	6.4	4.8
Total deferred income tax assets	44.6	48.1
Deferred income tax liabilities:
Depreciation and amortization	20.1	21.0
Pension	16.3	13.9
Intangible assets	16.8	16.8
Lease right-of-use assets	15.2	13.5
Other	3.0	3.0
Total deferred income tax liabilities	71.4	68.2
Net deferred income tax liabilities prior to valuation allowances	(26.8)	(20.1)
Valuation allowances	(6.2)	(4.8)
Net deferred income tax liability	$ (33.0)	$ (24.9)