Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents
Cash and money market funds		$ 26.8	$ 40.3
Commercial paper		46.1	32.2
Total		72.9	72.5
Trade Receivables – Net
Trade receivables, gross		143.0	117.5
Allowance for doubtful receivables		(0.8)	(0.8)
Trade receivables – net		142.2	116.7
Inventories
Finished products		70.1	79.5
Work-in-process		73.5	63.6
Raw materials		56.0	53.4
Operating supplies and repair and maintenance parts		24.0	23.1
Total		223.6	219.6
Prepaid Expenses and Other Current Assets
Current derivative assets		4.6	1.5
Current deferred tax assets		0.0	49.6
Prepaid taxes		1.1	0.0
Prepaid insurance		1.5	1.9
Short-term restricted cash		0.3	0.3
Other		3.4	3.4
Total	[1]	10.9	56.7
Property, Plant and Equipment – Net
Land and improvements		22.7	22.7
Buildings and leasehold improvements		84.8	71.8
Machinery and equipment		585.2	549.0
Construction in progress		47.3	48.5
Property, plant and equipment – gross		740.0	692.0
Accumulated depreciation		(221.7)	(196.9)
Assets held for sale		0.3	0.3
Property, plant and equipment – net		518.6	495.4
Other Assets
Restricted cash		11.7	10.9
Debt issuance costs on Revolving Credit Facility		1.1	1.3
Deferred compensation plan assets		8.3	7.3
Derivative Asset, Noncurrent		1.0	0.1
Total	[1]	22.1	19.6
Other Accrued Liabilities
Current derivative liabilities		2.7	14.1
Uncleared cash disbursements		4.5	8.0
Accrued income taxes and taxes payable		7.8	3.1
Accrued annual contribution to VEBAs		0.0	19.6
Accrued contingent contribution to Union VEBA		17.1	0.0
Short-term environmental accrual		1.4	1.6
Accrued interest		8.6	1.5
Short-term deferred revenue		0.2	1.2
Other		4.4	3.6
Total		46.7	52.7
Long-Term Liabilities
Derivative liabilities		0.5	2.1
Income tax liabilities		0.9	0.7
Workers’ compensation accruals		23.9	21.7
Long-term environmental accruals		16.1	17.0
Long-term asset retirement obligations		5.1	4.8
Deferred compensation liabilities		8.3	7.7
Long-term deferred revenue		0.2	0.3
Long-term capital leases		0.0	0.1
Long-term portion of contingent contribution to Union VEBA		12.8	29.9
Other long-term liabilities		3.4	3.2
Total		71.2	87.5
Billed
Trade Receivables – Net
Trade receivables, gross		142.8	116.8
Unbilled
Trade Receivables – Net
Trade receivables, gross		$ 0.2	$ 0.7

[1] See Note 1 for discussion of our adoption of ASU 2015-03 and ASU 2015-17 (as defined in Note 1).