Supplemental Balance Sheet Information (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash and Cash Equivalents.
Cash and money market funds	$ 107.9	$ 49.8
Commercial paper	165.5	0
Total	273.4	49.8	135.6	30.3
Trade Receivables.
Billed trade receivables	124.4	98.9
Unbilled trade receivables - Note 1	0.2	0.9
Trade receivables, gross	124.6	99.8
Allowance for doubtful receivables	(0.8)	(0.9)
Trade receivables, net	123.8	98.9
Inventories.
Finished products	59.9	75.9
Work-in-process	55.5	57.5
Raw materials	53.9	58.1
Operating supplies and repairs and maintenance parts	16.7	14.2
Total	186.0	205.7
Prepaid Expenses and Other Current Assets.
Current derivative assets - Notes 12 and 13	3.0	0
Current deferred tax assets	59.5	63.0
Current portion of option premiums paid - Notes 12 and 13	0.1	0.4
Short-term restricted cash	1.3	7.8
Prepaid taxes	2.1	3.8
Prepaid expenses	4.1	3.9
Total	70.1	78.9
Property, Plant, and Equipment - Net.
Land and improvements	22.6	22.6
Buildings and leasehold improvements	50.9	45.9
Machinery and equipment	400.4	356.7
Construction in progress	20.8	24.1
Active property, plant, and equipment, gross	494.7	449.3
Accumulated depreciation	(111.4)	(86.9)
Active property, plant, and equipment, net	383.3	362.4
Idled equipment	1.0	5.4
Property, plant, and equipment - net	384.3	367.8
Other Assets.
Derivative assets - Notes 12 and 13	55.5	46.2
Option premiums paid - Notes 12 and 13	0	0.1
Restricted cash	10.0	10.4
Long-term income tax receivable	2.9	2.8
Deferred financing costs	11.7	7.8
Available for sale securities	5.6	4.9
Other	0.3	0.1
Total	86.0	72.3
Other Accrued Liabilities.
Current derivative liabilities - Notes 12 and 13	3.1	14.8
Current portion of option premiums received - Notes 12 and 13	0.1	0.1
Accrued book overdraft (uncleared cash disbursement)	4.7	0
Accrued income taxes and taxes payable	3.1	2.6
Accrued annual VEBA contribution	20.0	0
Accrued freight	2.2	2.4
Short-term environmental accrual - Note 11	3.0	1.2
Accrued interest	3.7	2.3
Short-term deferred revenue - Note 1	6.7	13.5
Other	5.3	4.1
Total	51.9	41.0
Long-term Liabilities.
Derivative liabilities - Notes 12 and 13	63.5	55.5
Option premiums received - Notes 12 and 13	0	0.1
Income tax liabilities	15.1	13.4
Workers' compensation accruals	24.0	20.8
Long-term environmental accrual - Note 11	18.7	20.8
Long-term asset retirement obligations	3.8	3.8
Long-term deferred revenue - Note 1	0	3.3
Deferred compensation liability	5.8	5.1
Other long-term liabilities	3.6	3.2
Total	134.5	126.0
Long-term Debt. - Note 3
Senior notes	225.0	0
Cash convertible senior notes	155.3	148.0
Other notes payable	0	3.4
Total	$ 380.3	$ 151.4