Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Cash and Cash Equivalents
Cash and money market funds	$ 40.3	$ 29.5
Commercial paper	32.2	148.2
Total	72.5	177.7
Trade Receivables - Net
Billed trade receivables	116.8	128.7
Unbilled trade receivables	0.7	1.4
Trade receivables, gross	117.5	130.1
Allowance for doubtful receivables	(0.8)	(0.8)
Trade receivables - net	116.7	129.3
Inventories
Finished products	79.5	73.6
Work-in-process	63.6	66.7
Raw materials	53.4	54.2
Operating supplies and repair and maintenance parts	23.1	20.2
Total	219.6	214.7
Prepaid Expenses and Other Current Assets
Current derivative assets — Notes 10 and 11	1.5	85.7
Current deferred tax assets	49.6	86.4
Prepaid insurance	1.9	2.0
Short-term restricted cash	0.3	0.3
Other	3.4	4.2
Total	56.7	178.6
Property, Plant and Equipment - Net
Land and improvements	22.7	22.9
Buildings and leasehold improvements	71.8	63.8
Machinery and equipment	549.0	509.8
Construction in progress	48.5	25.2
Property, plant and equipment - gross	692.0	621.7
Accumulated depreciation	(196.9)	(166.8)
Assets held for sale	0.3	0.0
Property, plant and equipment - net	495.4	454.9
Other Assets
Restricted cash	10.9	10.0
Deferred financing costs	4.5	5.9
Deferred compensation plan assets	7.3	7.3
Derivative assets — Notes 10 and 11	0.1	0.0
Other	0.0	0.1
Total	22.8	23.3
Other Accrued Liabilities
Current derivative liabilities — Notes 10 and 11	14.1	94.9
Uncleared cash disbursements	8.0	9.1
Accrued income taxes and taxes payable	3.1	5.2
Accrued annual VEBA contribution	19.6	13.7
Short-term environmental accrual — Note 9	1.6	2.3
Accrued interest	1.5	3.7
Short-term deferred revenue — Note 1	1.2	0.2
Other	3.6	3.7
Total	52.7	132.8
Long-Term Liabilities
Derivative liabilities — Notes 10 and 11	2.1	1.9
Income tax liabilities	0.7	2.4
Workers’ compensation accruals	21.7	21.5
Long-term environmental accrual — Note 9	17.0	17.0
Long-term asset retirement obligations	4.8	4.4
Long-term deferred revenue - Note 1	0.3	0.5
Deferred compensation liability	7.7	7.2
Long-term capital leases	0.1	0.1
Long-term portion of contingent contribution to Union VEBA – Note 6	29.9	0.0
Other long-term liabilities	3.2	3.3
Total	$ 87.5	$ 58.3