Supplemental Balance Sheet Information - Schedule of Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Trade Receivables, Net
Allowance for doubtful receivables	$ (0.5)	$ (0.5)
Trade receivables, net	363.6	297.2
Inventories
Finished products	105.0	98.0
Work-in-process	208.8	242.5
Raw materials	171.3	174.0
Operating supplies	12.8	10.9
Inventories	497.9	525.4
Property, Plant and Equipment, Net
Land and improvements	37.9	28.4
Buildings and leasehold improvements	196.4	185.5
Machinery and equipment	1,254.8	1,232.7
Construction in progress	175.6	141.3
Property, plant and equipment, gross	1,664.7	1,587.9
Accumulated depreciation and amortization	(623.7)	(574.9)
Assets held for sale		0.2
Property, plant and equipment, net	1,041.0	1,013.2
Other Accrued Liabilities
Uncleared cash disbursements	13.4	13.6
Accrued income taxes and other taxes payable	9.7	8.9
Accrued interest	10.0	9.9
Short-term environmental accrual - Note 7	1.0	1.1
Short-term operating lease liabilities	9.3	9.1
Short-term finance lease liabilities	2.0	2.1
Other - Note 5	25.0	23.7
Other accrued liabilities	70.4	68.4
Long-Term Liabilities
Workers' compensation accrual	32.1	30.9
Long-term environmental accrual - Note 7	17.2	16.6
Other long-term liabilities	36.6	27.2
Long-term liabilities	85.9	74.7
Billed
Trade Receivables, Net
Billed trade receivables	$ 364.1	$ 297.7