Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets
Net operating loss carryforwards	$ 21.4	$ 21.9
Tax credit carryforwards	2.0	2.8
Restructuring and impairment charges	0.4	0.0
Pension and deferred compensation	35.3	25.6
Other	10.6	9.2
Valuation allowance	(15.1)	(15.9)
Total deferred tax assets	54.6	43.6
Deferred tax liabilities:
Property, plant, and equipment	42.1	37.9
Tax on undistributed earnings of subsidiaries	6.5	6.3
Other	0.4	0.9
Total deferred tax liabilities	49.0	45.1
Net deferred tax (liability) asset	$ 5.6
Net deferred tax (liability) asset		$ (1.5)