Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents
Cash and money market funds	$ 30.7	$ 37.9
Commercial paper	26.4	17.3
Total	57.1	55.2
Trade Receivables – Net
Trade receivables, gross	146.7	138.5
Allowance for doubtful receivables	(1.1)	(0.8)
Trade receivables – net	145.6	137.7
Inventories
Finished products	60.7	73.8
Work-in-process	81.2	71.7
Raw materials	53.4	51.1
Operating supplies	4.6	5.0
Total	199.9	201.6
Property, Plant and Equipment – Net
Land and improvements	22.8	22.7
Buildings and leasehold improvements	90.0	88.6
Machinery and equipment	625.0	615.1
Construction in progress	62.4	34.8
Property, plant and equipment – gross	800.2	761.2
Accumulated depreciation	(248.4)	(230.6)
Assets held for sale	0.3	0.3
Property, plant and equipment – net	552.1	530.9
Other Accrued Liabilities
Uncleared cash disbursements	8.2	5.8
Accrued income taxes and taxes payable	7.7	4.3
Accrued annual contribution to VEBAs	11.5	20.0
Accrued interest	2.9	2.9
Other	7.2	7.1
Total	37.5	40.1
Long-Term Liabilities
Workers’ compensation accruals	24.5	25.0
Long-term environmental accrual	15.8	15.8
Long-term portion of contingent contribution to Union VEBA	0.0	12.8
Other long-term liabilities	20.8	19.6
Total	61.1	73.2
Billed
Trade Receivables – Net
Trade receivables, gross	146.4	138.2
Unbilled
Trade Receivables – Net
Trade receivables, gross	$ 0.3	$ 0.3