Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Measurement of assets and liabilities at fair value on a recurring basis
Derivative liability for conversion feature associated with convertible debt		$ 26,440
Fair Value, Measurements, Recurring
Measurement of assets and liabilities at fair value on a recurring basis
Derivative liability for conversion feature associated with convertible debt		26,440
Fair Value, Measurements, Recurring | Level 1
Measurement of assets and liabilities at fair value on a recurring basis
Derivative liability for conversion feature associated with convertible debt		0
Fair Value, Measurements, Recurring | Level 2
Measurement of assets and liabilities at fair value on a recurring basis
Derivative liability for conversion feature associated with convertible debt		0
Fair Value, Measurements, Recurring | Level 3
Measurement of assets and liabilities at fair value on a recurring basis
Derivative liability for conversion feature associated with convertible debt		26,440
Forward Contracts | Not Designated as Hedging Instrument | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability for commodity hedges	2,494	2,331
Forward Contracts | Not Designated as Hedging Instrument | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability for commodity hedges	0	0
Forward Contracts | Not Designated as Hedging Instrument | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability for commodity hedges	2,494	2,331
Forward Contracts | Not Designated as Hedging Instrument | Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability for commodity hedges	$ 0	$ 0