Annual report pursuant to Section 13 and 15(d)

Share-Based and Cash-Based Incentive Compensation - Outstanding Restricted Shares Issued to Non-employee Directors (Details)

v2.4.1.9
Share-Based and Cash-Based Incentive Compensation - Outstanding Restricted Shares Issued to Non-employee Directors (Details) (Restricted Shares)
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Awards expected to vest by period 43,210us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber 43,840us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber 43,687us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber 51,870us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
2015        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Awards expected to vest by period 21,520us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ us-gaap_VestingAxis
= wti_TwoThousandFifteenMember 		     
2016        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Awards expected to vest by period 15,420us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ us-gaap_VestingAxis
= wti_TwoThousandSixteenMember 		     
2017        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Awards expected to vest by period 6,270us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ us-gaap_VestingAxis
= wti_TwoThousandAndSeventeenMember