Derivatives, Hedges, Financial Instruments and Carbon Credits (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Liabilities - Current and noncurrent accrued and other liabilities:
Total	$ 2,282	$ 2,283
Recurring [Member]
Assets - Supplies, prepaid items and other:
Total	332	53
Liabilities - Current and noncurrent accrued and other liabilities:
Total	2,282	2,283
Recurring [Member] | Commodities Contracts [Member]
Assets - Supplies, prepaid items and other:
Derivative Assets	108	11
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities	23
Recurring [Member] | Carbon Credits [Member]
Assets - Supplies, prepaid items and other:
Carbon credits	224	42
Liabilities - Current and noncurrent accrued and other liabilities:
Contractual obligations - carbon credits	224	42
Recurring [Member] | Interest Rate Contracts [Member]
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities	2,035	2,241
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets - Supplies, prepaid items and other:
Total	108
Liabilities - Current and noncurrent accrued and other liabilities:
Total	23
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commodities Contracts [Member]
Assets - Supplies, prepaid items and other:
Derivative Assets	108
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities	23
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Carbon Credits [Member]
Assets - Supplies, prepaid items and other:
Carbon credits
Liabilities - Current and noncurrent accrued and other liabilities:
Contractual obligations - carbon credits
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Interest Rate Contracts [Member]
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets - Supplies, prepaid items and other:
Total
Liabilities - Current and noncurrent accrued and other liabilities:
Total	2,035
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commodities Contracts [Member]
Assets - Supplies, prepaid items and other:
Derivative Assets
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Carbon Credits [Member]
Assets - Supplies, prepaid items and other:
Carbon credits
Liabilities - Current and noncurrent accrued and other liabilities:
Contractual obligations - carbon credits
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Contracts [Member]
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities	2,035
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets - Supplies, prepaid items and other:
Total	224
Liabilities - Current and noncurrent accrued and other liabilities:
Total	224
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commodities Contracts [Member]
Assets - Supplies, prepaid items and other:
Derivative Assets
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Carbon Credits [Member]
Assets - Supplies, prepaid items and other:
Carbon credits	224
Liabilities - Current and noncurrent accrued and other liabilities:
Contractual obligations - carbon credits	224
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Interest Rate Contracts [Member]
Liabilities - Current and noncurrent accrued and other liabilities:
Derivative Financial Instruments, Liabilities