Annual report pursuant to Section 13 and 15(d)

Acquisitions and Divestitures - Business Acquisition Pro Forma Information Incremental Items (Parenthetical) (Details)

v2.4.1.9
Acquisitions and Divestitures - Business Acquisition Pro Forma Information Incremental Items (Parenthetical) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2013
Business Acquisition [Line Items]        
Long-term debt, less current maturities $ 1,360,057us-gaap_LongTermDebtNoncurrent $ 1,205,421us-gaap_LongTermDebtNoncurrent   $ 1,205,421us-gaap_LongTermDebtNoncurrent
Federal statutory income tax rate 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate  
Woodside Properties        
Business Acquisition [Line Items]        
Long-term debt, less current maturities 54,800us-gaap_LongTermDebtNoncurrent
/ us-gaap_BusinessAcquisitionAxis
= wti_WoodsidePropertiesMember 		     
Effective interest rate 1.80%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_BusinessAcquisitionAxis
= wti_WoodsidePropertiesMember 		     
Federal statutory income tax rate 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
/ us-gaap_BusinessAcquisitionAxis
= wti_WoodsidePropertiesMember 		     
Callon Properties        
Business Acquisition [Line Items]        
Long-term debt, less current maturities   83,000us-gaap_LongTermDebtNoncurrent
/ us-gaap_BusinessAcquisitionAxis
= wti_CallonPropertiesMember 		  83,000us-gaap_LongTermDebtNoncurrent
/ us-gaap_BusinessAcquisitionAxis
= wti_CallonPropertiesMember
Effective interest rate   2.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_BusinessAcquisitionAxis
= wti_CallonPropertiesMember 		  2.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_BusinessAcquisitionAxis
= wti_CallonPropertiesMember
Federal statutory income tax rate       35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
/ us-gaap_BusinessAcquisitionAxis
= wti_CallonPropertiesMember
Newfield Properties        
Business Acquisition [Line Items]        
Long-term debt, less current maturities     205,800us-gaap_LongTermDebtNoncurrent
/ us-gaap_BusinessAcquisitionAxis
= wti_NewfieldPropertiesMember 		 
Effective interest rate     7.70%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_BusinessAcquisitionAxis
= wti_NewfieldPropertiesMember 		 
Federal statutory income tax rate     35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
/ us-gaap_BusinessAcquisitionAxis
= wti_NewfieldPropertiesMember