Supplemental Balance Sheet Information - Schedule of Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Trade Receivables, Net
Allowance for doubtful receivables	$ (0.6)	$ (0.5)
Trade receivables, net	365.0	297.2
Inventories
Finished products	124.8	98.0
Work-in-process	183.0	242.5
Raw materials	217.9	174.0
Operating supplies	12.0	10.9
Total	537.7	525.4
Property, Plant and Equipment, Net
Land and improvements	37.9	28.4
Buildings and leasehold improvements	195.5	185.5
Machinery and equipment	1,243.6	1,232.7
Construction in progress	159.8	141.3
Property, plant and equipment, gross	1,636.8	1,587.9
Accumulated depreciation and amortization	(599.0)	(574.9)
Assets held for sale		0.2
Property, plant and equipment, net	1,037.8	1,013.2
Other Accrued Liabilities
Uncleared cash disbursements	25.1	13.6
Accrued income taxes and other taxes payable	13.5	8.9
Accrued interest	10.5	9.9
Short-term environmental accrual - Note 7	1.0	1.1
Short-term operating lease liabilities	9.2	9.1
Other - Note 5	21.6	25.8
Total	80.9	68.4
Long-Term Liabilities
Workers' compensation accrual	30.5	30.9
Long-term environmental accrual - Note 7	16.5	16.6
Other long-term liabilities	35.8	27.2
Total	82.8	74.7
Billed
Trade Receivables, Net
Billed trade receivables	$ 365.6	$ 297.7