Annual report pursuant to Section 13 and 15(d)

Derivative Financial Instruments - Estimated Fair Value of Derivative Contracts (Details)

v2.4.1.9
Derivative Financial Instruments - Estimated Fair Value of Derivative Contracts (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2013
Derivatives Fair Value [Line Items]  
Fair value of commodity derivative contracts $ 141us-gaap_DerivativeFairValueOfDerivativeAsset
Fair value of commodity derivative contracts 9,423us-gaap_DerivativeFairValueOfDerivativeLiability
Prepaid And Other Assets  
Derivatives Fair Value [Line Items]  
Fair value of commodity derivative contracts 141us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherCurrentAssetsMember
Accrued Liabilities  
Derivatives Fair Value [Line Items]  
Fair value of commodity derivative contracts $ 9,423us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_InformationByFinancialStatementLineItemAxis
= us-gaap_AccruedLiabilitiesMember