Quarterly report pursuant to Section 13 or 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
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Business Acquisition [Line Items]      
Long-term debt, less current maturities $ 1,426,437us-gaap_LongTermDebtNoncurrent   $ 1,360,057us-gaap_LongTermDebtNoncurrent
Federal statutory income tax rate 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