Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents
Cash and money market funds	$ 17.3	$ 37.9
Commercial paper	56.6	17.3
Total	73.9	55.2
Trade Receivables – Net
Trade receivables, gross	139.0	138.5
Allowance for doubtful receivables	(0.8)	(0.8)
Trade receivables – net	138.2	137.7
Inventories
Finished products	64.8	73.8
Work-in-process	86.1	71.7
Raw materials	56.9	51.1
Operating supplies	4.4	5.0
Total	212.2	201.6
Property, Plant and Equipment – Net
Land and improvements	22.7	22.7
Buildings and leasehold improvements	90.2	88.6
Machinery and equipment	675.0	615.1
Construction in progress	27.8	34.8
Property, plant and equipment – gross	815.7	761.2
Accumulated depreciation	(258.2)	(230.6)
Assets held for sale	0.3	0.3
Property, plant and equipment – net	557.8	530.9
Other Accrued Liabilities
Uncleared cash disbursements	7.1	5.8
Accrued income taxes and taxes payable	9.0	4.3
Accrued annual contribution to VEBAs	12.0	20.0
Accrued interest	8.4	2.9
Other	6.8	7.1
Total	43.3	40.1
Long-Term Liabilities
Workers’ compensation accruals	25.0	25.0
Long-term environmental accrual	16.1	15.8
Long-term portion of contingent contribution to Union VEBA	0.0	12.8
Other long-term liabilities	20.8	19.6
Total	61.9	73.2
Billed
Trade Receivables – Net
Trade receivables, gross	138.8	138.2
Unbilled
Trade Receivables – Net
Trade receivables, gross	$ 0.2	$ 0.3