Supplemental Balance Sheet Information - Schedule of Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Trade Receivables, Net
Allowance for doubtful receivables	$ (0.6)	$ (0.8)
Trade receivables, net	432.2	332.7
Inventories
Finished products	83.7	90.3
Work-in-process	169.2	162.2
Raw materials	169.0	143.0
Operating supplies	9.6	9.1
Total	431.5	404.6
Property, Plant and Equipment, Net
Land and improvements	26.5	26.0
Buildings and leasehold improvements	182.5	179.0
Machinery and equipment	1,160.4	1,151.5
Construction in progress	89.8	75.3
Property, plant and equipment, gross	1,459.2	1,431.8
Accumulated depreciation and amortization	(503.4)	(480.4)
Assets held for sale	4.4	3.8
Property, plant and equipment, net	960.2	955.2
Other Accrued Liabilities
Uncleared cash disbursements	16.7	10.9
Accrued income taxes and other taxes payable	16.3	9.5
Accrued interest	10.3	9.9
Short-term environmental accrual	2.3	2.6
Other	25.3	25.5
Total	70.9	58.4
Long-Term Liabilities
Workers' compensation accrual	31.8	31.9
Long-term environmental accrual	14.1	14.2
Other long-term liabilities	28.5	26.4
Total	74.4	72.5
Billed
Trade Receivables, Net
Billed trade receivables	$ 432.8	$ 333.5