Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents
Cash and money market funds	$ 29.3	$ 22.9
Commercial paper	86.0	102.7
Total	115.3	125.6
Trade Receivables – Net
Trade receivables, gross	196.6	180.6
Allowance for doubtful receivables	(0.8)	(0.8)
Trade receivables – net	195.8	179.8
Inventories
Finished products	47.1	48.0
Work-in-process	104.9	85.6
Raw materials	74.8	75.0
Operating supplies	7.1	6.5
Total	233.9	215.1
Property, Plant and Equipment – Net
Land and improvements	21.4	21.4
Buildings and leasehold improvements	97.8	97.0
Machinery and equipment	766.9	755.6
Construction in progress	41.8	43.6
Property, plant and equipment – gross	927.9	917.6
Accumulated depreciation	(318.6)	(307.4)
Assets held for sale	1.6	1.6
Property, plant and equipment – net	610.9	611.8
Other Accrued Liabilities
Uncleared cash disbursements	6.6	4.8
Accrued income taxes and taxes payable	9.9	6.5
Accrued annual contribution to Salaried VEBA	0.0	2.1
Accrued interest	8.4	2.9
Other	26.7	27.7
Total	51.6	44.0
Long-Term Liabilities
Workers’ compensation accruals	25.5	24.6
Long-term environmental accrual	13.1	14.3
Other long-term liabilities	23.2	27.5
Total	61.8	66.4
Billed
Trade Receivables – Net
Trade receivables, gross	196.6	179.5
Unbilled
Trade Receivables – Net
Trade receivables, gross	$ 0.0	$ 1.1