Supplemental Balance Sheet Information - Schedule of Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Trade Receivables, Net
Allowance for doubtful receivables	$ (0.6)	$ (0.8)
Trade receivables, net	351.1	332.7
Inventories
Finished products	66.9	90.3
Work-in-process	160.3	162.2
Raw materials	230.2	143.0
Operating supplies	11.2	9.1
Total	468.6	404.6
Property, Plant and Equipment, Net
Land and improvements	26.4	26.0
Buildings and leasehold improvements	184.5	179.0
Machinery and equipment	1,171.7	1,151.5
Construction in progress	99.8	75.3
Property, plant and equipment, gross	1,482.4	1,431.8
Accumulated depreciation and amortization	(526.5)	(480.4)
Assets held for sale	0.4	3.8
Property, plant and equipment, net	956.3	955.2
Other Accrued Liabilities
Uncleared cash disbursements	11.1	10.9
Accrued income taxes and other taxes payable	11.7	9.5
Accrued interest	9.9	9.9
Short-term environmental accrual	2.8	2.6
Other	51.8	25.5
Total	87.3	58.4
Long-Term Liabilities
Workers' compensation accrual	31.8	31.9
Long-term environmental accrual	13.2	14.2
Other long-term liabilities	28.6	26.4
Total	73.6	72.5
Billed
Trade Receivables, Net
Billed trade receivables	$ 351.7	$ 333.5