Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation and Cash-Based Incentive Compensation - Schedule of Restricted Stock Units Outstanding (Parenthetical) (Details)

v2.4.1.9
Share-Based Compensation and Cash-Based Incentive Compensation - Schedule of Restricted Stock Units Outstanding (Parenthetical) (Details) (Restricted Stock Units (RSUs), 2015, Restricted Stock Units subject to service and other requirements)
 3 Months Ended
Mar. 31, 2015
Restricted Stock Units (RSUs) | 2015 | Restricted Stock Units subject to service and other requirements
  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Restricted stock units adjustments, percentage 0.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMinimum
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_IncomeStatementLocationAxis
= wti_RestrictedStockUnitsSubjectToMarketPerformanceMetricsAndServiceRequirementsMember
/ us-gaap_VestingAxis
= wti_TwoThousandFifteenMember
Restricted stock units adjustments, percentage 200.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_IncomeStatementLocationAxis
= wti_RestrictedStockUnitsSubjectToMarketPerformanceMetricsAndServiceRequirementsMember
/ us-gaap_VestingAxis
= wti_TwoThousandFifteenMember