Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents
Cash and money market funds	$ 28.2	$ 22.9
Commercial paper	236.1	102.7
Cash and Cash Equivalents, at Carrying Value	264.3	125.6	$ 51.1
Trade Receivables - Net
Billed trade receivables	168.5	179.5
Unbilled trade receivables	0.0	1.1
Trade receivables, gross	168.5	180.6
Allowance for doubtful receivables	(1.4)	(0.8)
Trade receivables - net	167.1	179.8
Inventories
Finished products	42.6	48.0
Work-in-process	63.5	85.6
Raw materials	65.0	75.0
Operating supplies	6.5	6.5
Total	177.6	215.1
Property, Plant and Equipment - Net
Land and improvements	21.4	21.4
Buildings and leasehold improvements	104.5	97.0
Machinery and equipment	813.5	755.6
Construction in progress	33.2	43.6
Property, plant and equipment - gross	972.6	917.6
Accumulated depreciation	(352.2)	(307.4)
Assets held for sale	1.6	1.6
Property, plant and equipment - net	622.0	611.8
Other Accrued Liabilities
Uncleared cash disbursements	4.2	4.8
Accrued income taxes and taxes payable	6.2	6.5
Accrued annual contribution to VEBAs – Note 5	2.9	2.1
Accrued interest	2.3	2.9
Short-term environmental accrual	5.5	2.6
Other	22.9	25.1
Total	44.0	44.0
Long-Term Liabilities
Workers’ compensation accruals	27.7	24.6
Long-term environmental accrual – Note 10	11.5	14.3
Other long-term liabilities	27.8	27.5
Total	$ 67.0	$ 66.4