Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents
Cash and money market funds		$ 34.5	$ 40.3
Commercial paper		36.2	32.2
Total		70.7	72.5
Trade Receivables – Net
Trade receivables, gross		139.6	117.5
Allowance for doubtful receivables		(0.8)	(0.8)
Trade receivables – net		138.8	116.7
Inventories
Finished products		66.8	79.5
Work-in-process		73.4	63.6
Raw materials		46.7	53.4
Operating supplies and repair and maintenance parts		23.7	23.1
Total		210.6	219.6
Prepaid Expenses and Other Current Assets
Current derivative assets – Notes 8 and 9		1.4	1.5
Current deferred tax assets		0.0	49.6
Short-term restricted cash		0.3	0.3
Prepaid taxes		3.3	0.0
Prepaid Insurance		1.1	1.9
Other		3.0	3.4
Total	[1]	9.1	56.7
Property, Plant and Equipment – Net
Land and improvements		22.7	22.7
Buildings and leasehold improvements		72.5	71.8
Machinery and equipment		559.3	549.0
Construction in progress		54.8	48.5
Property, plant and equipment – gross		709.3	692.0
Accumulated depreciation		(205.1)	(196.9)
Assets held for sale		0.3	0.3
Property, plant and equipment – net		504.5	495.4
Other Assets
Restricted cash		10.9	10.9
Deferred financing costs		1.1	1.3
Deferred compensation plan assets		7.3	7.3
Derivative Asset, Noncurrent		0.2	0.1
Total	[1]	19.5	19.6
Other Accrued Liabilities
Current derivative liabilities – Notes 8 and 9		10.3	14.1
Uncleared cash disbursements		10.0	8.0
Accrued income taxes and taxes payable		8.6	3.1
Accrued annual contribution to VEBAs		0.0	19.6
Accrued contingent contribution to Union VEBA – Note 5		17.1	0.0
Short-term environmental accrual – Note 7		1.3	1.6
Accrued interest		5.5	1.5
Short-term deferred revenue		0.8	1.2
Other		2.9	3.6
Total		56.5	52.7
Long-Term Liabilities
Derivative liabilities – Notes 8 and 9		1.7	2.1
Income tax liabilities		0.8	0.7
Workers’ compensation accruals		24.1	21.7
Long-term environmental accruals – Note 7		16.8	17.0
Long-term asset retirement obligations		4.9	4.8
Deferred compensation liabilities		7.8	7.7
Long-term deferred revenue		0.3	0.3
Long-term capital leases		0.1	0.1
Long-term portion of contingent contribution to Union VEBA – Note 5		12.8	29.9
Other long-term liabilities		3.2	3.2
Total		72.5	87.5
Billed
Trade Receivables – Net
Trade receivables, gross		139.4	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, ASU 2015-15 and ASU 2015-17 (as defined in Note 1).