Annual report pursuant to Section 13 and 15(d)

Asset Retirement Obligations - Reconciliation of Asset Retirement Obligations Liability (Details)

v2.4.1.9
Asset Retirement Obligations - Reconciliation of Asset Retirement Obligations Liability (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset retirement obligations, beginning of period $ 354,422us-gaap_AssetRetirementObligation $ 384,053us-gaap_AssetRetirementObligation  
Asset retirement obligation settlements (74,313)us-gaap_AssetRetirementObligationCashPaidToSettle (81,543)us-gaap_AssetRetirementObligationCashPaidToSettle (112,827)us-gaap_AssetRetirementObligationCashPaidToSettle
Accretion of discount 20,633us-gaap_AssetRetirementObligationAccretionExpense 20,918us-gaap_AssetRetirementObligationAccretionExpense 20,055us-gaap_AssetRetirementObligationAccretionExpense
Disposition of properties   (19,564)wti_AssetRetirementObligationsDispositionOfProperties  
Liabilities assumed through acquisition 21,820wti_AssetRetirementObligationsLiabilitiesAssumedThroughAcquisition 4,233wti_AssetRetirementObligationsLiabilitiesAssumedThroughAcquisition  
Liabilities incurred 3,258us-gaap_AssetRetirementObligationLiabilitiesIncurred 1,745us-gaap_AssetRetirementObligationLiabilitiesIncurred  
Revisions of estimated liabilities 64,748us-gaap_AssetRetirementObligationRevisionOfEstimate 44,580us-gaap_AssetRetirementObligationRevisionOfEstimate  
Asset retirement obligations, end of period 390,568us-gaap_AssetRetirementObligation 354,422us-gaap_AssetRetirementObligation 384,053us-gaap_AssetRetirementObligation
Less current portion 36,003us-gaap_AssetRetirementObligationCurrent 77,785us-gaap_AssetRetirementObligationCurrent  
Long-term $ 354,565us-gaap_AssetRetirementObligationsNoncurrent $ 276,637us-gaap_AssetRetirementObligationsNoncurrent