Supplemental Balance Sheet Information (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Trade Receivables.
Billed trade receivables	$ 128.1	$ 98.9
Unbilled trade receivables - Note 1	4.1	0.9
Trade receivables, gross	132.2	99.8
Allowance for doubtful receivables	(0.9)	(0.9)
Trade receivables, net	131.3	98.9
Inventories.
Finished products	62.0	75.9
Work in process	66.8	57.5
Raw materials	52.3	58.1
Operating supplies and repairs and maintenance parts	15.7	14.2
Total	196.8	205.7
Prepaid Expenses and Other Current Assets.
Current derivative assets - Notes 10 and 11	1.4	0
Current deferred tax assets	63.0	63.0
Current portion of option premiums paid - Notes 10 and 11	0.3	0.4
Short-term restricted cash	0.9	7.8
Prepaid taxes	3.0	3.8
Prepaid expenses	6.1	3.9
Total	74.7	78.9
Property, Plant and Equipment - Net.
Land and improvements	22.6	22.6
Buildings and leasehold improvements	49.8	45.9
Machinery and equipment	379.1	356.7
Construction in progress	15.0	24.1
Active property, plant and equipment, gross	466.5	449.3
Accumulated depreciation	(98.9)	(86.9)
Active property, plant and equipment, net	367.6	362.4
Idled equipment	5.4	5.4
Total	373.0	367.8
Other Assets.
Derivative assets - Notes 10 and 11	42.0	46.2
Option premiums paid - Notes 10 and 11	0.1	0.1
Restricted cash	10.1	10.4
Long-term income tax receivable	2.8	2.8
Deferred financing costs	13.0	7.8
Available for sale securities	5.5	4.9
Other	0.3	0.1
Total	73.8	72.3
Other Accrued Liabilities.
Current derivative liabilities - Notes 10 and 11	13.5	14.8
Current portion of option premiums received - Notes 10 and 11	0.1	0.1
Accrued book overdraft (uncleared cash disbursement)	6.2	0
Taxes payable	4.5	2.6
Accrued freight	2.8	2.4
Short-term environmental accrual - Note 9	1.7	1.2
Accrued interest	4.1	2.3
Short-term deferred revenue - Note 1	9.0	13.5
Other	4.4	4.1
Total	46.3	41.0
Long-term Liabilities.
Derivative liabilities - Notes 10 and 11	49.9	55.5
Option premiums received - Notes 10 and 11	0.1	0.1
Income tax liabilities	13.7	13.4
Workers' compensation accruals	20.6	20.8
Long-term environmental accrual - Note 9	20.3	20.8
Long-term asset retirement obligations	4.0	3.8
Long-term deferred revenue - Note 1	1.6	3.3
Deferred compensation liability	5.6	5.1
Other long-term liabilities	2.9	3.2
Total	$ 118.7	$ 126.0