Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents
Cash and money market funds		$ 50.6	$ 40.3
Commercial paper		144.7	32.2
Total		195.3	72.5
Trade Receivables – Net
Trade receivables, gross		135.4	117.5
Allowance for doubtful receivables		(0.8)	(0.8)
Trade receivables – net		134.6	116.7
Inventories
Finished products		65.2	79.5
Work-in-process		78.8	63.6
Raw materials		49.9	53.4
Operating supplies and repair and maintenance parts		23.6	23.1
Total		217.5	219.6
Prepaid Expenses and Other Current Assets
Current derivative assets		4.6	1.5
Current deferred tax assets		0.0	49.6
Short-term restricted cash		0.3	0.3
Prepaid taxes		2.2	0.0
Prepaid Insurance		2.1	1.9
Other		3.6	3.4
Total	[1]	12.8	56.7
Property, Plant and Equipment – Net
Land and improvements		22.7	22.7
Buildings and leasehold improvements		83.6	71.8
Machinery and equipment		573.8	549.0
Construction in progress		45.7	48.5
Property, plant and equipment – gross		725.8	692.0
Accumulated depreciation		(213.4)	(196.9)
Assets held for sale		0.3	0.3
Property, plant and equipment – net		512.7	495.4
Other Assets
Restricted cash		11.0	10.9
Deferred financing costs		1.1	1.3
Deferred compensation plan assets		7.8	7.3
Derivative Asset, Noncurrent		0.8	0.1
Total	[1]	20.7	19.6
Other Accrued Liabilities
Current derivative liabilities		4.3	14.1
Uncleared cash disbursements		7.8	8.0
Accrued income taxes and taxes payable		6.7	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		3.1	1.5
Short-term deferred revenue		0.2	1.2
Other		3.6	3.6
Total		44.2	52.7
Long-Term Liabilities
Derivative liabilities		0.7	2.1
Income tax liabilities		0.8	0.7
Workers’ compensation accruals		24.0	21.7
Long-term environmental accruals		16.4	17.0
Long-term asset retirement obligations		5.0	4.8
Deferred compensation liabilities		8.0	7.7
Long-term deferred revenue		0.2	0.3
Long-term capital leases		0.1	0.1
Long-term portion of contingent contribution to Union VEBA		12.8	29.9
Other long-term liabilities		3.4	3.2
Total		71.4	87.5
Billed
Trade Receivables – Net
Trade receivables, gross		135.2	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).