Annual report pursuant to Section 13 and 15(d)

Contingencies - Additional Information (Details)

v2.4.1.9
Contingencies - Additional Information (Details) (USD $)
 1 Months Ended 3 Months Ended 12 Months Ended
Jan. 31, 2014
Mar. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 15, 2014
Dec. 31, 2010
Loss Contingencies [Line Items]              
Underpayment of royalties $ 30,000wti_UnderPaymentOfRoyalty            
Under payment percentage of total royalty payments 0.0045%wti_UnderPaymentOfRoyaltyPercentage            
Statutory fine payment relative to underpayment   2,300,000us-gaap_LossContingencyDamagesAwardedValue          
Loss contingency, range of possible loss, minimum           0us-gaap_LossContingencyRangeOfPossibleLossMinimum  
Loss contingency, range of possible loss, maximum           32,000,000us-gaap_LossContingencyRangeOfPossibleLossMaximum  
Insurance claims submitted for removal-of-wreck expenses     43,000,000wti_ClaimsSubmittedRelatedToRemovalOfWreckExpenses        
Notified disallowed amount in reductions taken by ONRR             4,700,000us-gaap_GainContingencyUnrecordedAmount
Settlement of lawsuits, fines, penalties and other     400,000wti_SettlementsOfLegalMattersFinesAndPenalties 500,000wti_SettlementsOfLegalMattersFinesAndPenalties 9,300,000wti_SettlementsOfLegalMattersFinesAndPenalties    
Liability loss contingency     100,000us-gaap_LossContingencyAccrualAtCarryingValue 200,000us-gaap_LossContingencyAccrualAtCarryingValue      
Liberty Mutual Insurance Co              
Loss Contingencies [Line Items]              
Insurance claims received     5,000,000us-gaap_LossContingencyRelatedReceivableCarryingValueReceipts
/ dei_LegalEntityAxis
= wti_LibertyMutualInsuranceCoMember 		       
Revised estimate              
Loss Contingencies [Line Items]              
Insurance claims receivable     31,000,000us-gaap_LossContingencyReceivable
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember 		       
Comprehensive General Liability policy              
Loss Contingencies [Line Items]              
Insurance claims received     1,000,000us-gaap_LossContingencyRelatedReceivableCarryingValueReceipts
/ us-gaap_ScheduleOfMalpracticeInsuranceTypeAndTierIdentifierAxis
= us-gaap_GeneralLiabilityMember 		       
Energy Package              
Loss Contingencies [Line Items]              
Insurance claims received     1,000,000us-gaap_LossContingencyRelatedReceivableCarryingValueReceipts
/ us-gaap_ScheduleOfMalpracticeInsuranceTypeAndTierIdentifierAxis
= wti_EnergyPackageMember 		       
Starr Marine              
Loss Contingencies [Line Items]              
Insurance claims received     $ 5,000,000us-gaap_LossContingencyRelatedReceivableCarryingValueReceipts
/ us-gaap_ScheduleOfMalpracticeInsuranceTypeAndTierIdentifierAxis
= wti_StarrMarineMember