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Incentive Compensation Plan and Directors Compensation Plan - Additional Information (Details) (USD $)
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12 Months Ended | ||
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Compensation Plan [Line Items] | |||
| Share based compensation performance awards grant performance period | 10 years | ||
| Annual incentive awards payment period | 90 days | ||
| Percentage of restricted stock units granted not subject to performance criteria | 3.00%wti_PercentageOfRestrictedStockUnitsGrantedDuringPeriodNotSubjectToPerformanceCriteria | ||
| Expected vesting month and year | 2014-12 | ||
| Cash based compensation payment period | 75 days | ||
| 2014 Annual Incentive Plan Award | Chief Executive Officer | |||
| Compensation Plan [Line Items] | |||
| Common stock pre-determined price per share |
14.66us-gaap_SharePrice / us-gaap_PlanNameAxis = wti_TwoThousandFourteenAnnualIncentivePlanAwardMember / us-gaap_TitleOfIndividualAxis = us-gaap_ChiefExecutiveOfficerMember |
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| Directors Compensation Plan Share-Based Awards | Restricted Shares | |||
| Compensation Plan [Line Items] | |||
| Vesting rights description | Vesting occurs upon completion of the specified vesting period and one-third of each grant vests each year over a three-year period. | ||
| Grant vesting period | 3 years | 3 years | 3 years |
| Adjusted EBITDA and Adjusted EBITDA Margin | |||
| Compensation Plan [Line Items] | |||
| Restricted stock units earning per share, minimum |
0.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMinimum / us-gaap_VestingAxis = wti_AdjustedEBITDAAndAdjustedEBITDAMarginPerformanceStockAwardsMember |
0.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMinimum / us-gaap_VestingAxis = wti_AdjustedEBITDAAndAdjustedEBITDAMarginPerformanceStockAwardsMember |
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| Restricted stock units earning per share, maximum |
100.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMaximum / us-gaap_VestingAxis = wti_AdjustedEBITDAAndAdjustedEBITDAMarginPerformanceStockAwardsMember |
150.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMaximum / us-gaap_VestingAxis = wti_AdjustedEBITDAAndAdjustedEBITDAMarginPerformanceStockAwardsMember |
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| Shareholder Return Performance Stock Awards | |||
| Compensation Plan [Line Items] | |||
| Restricted stock units earning per share, minimum |
0.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMinimum / us-gaap_VestingAxis = wti_ShareholderReturnPerformanceStockAwardsMember |
0.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMinimum / us-gaap_VestingAxis = wti_ShareholderReturnPerformanceStockAwardsMember |
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| Restricted stock units earning per share, maximum |
200.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMaximum / us-gaap_VestingAxis = wti_ShareholderReturnPerformanceStockAwardsMember |
150.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMaximum / us-gaap_VestingAxis = wti_ShareholderReturnPerformanceStockAwardsMember |
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| Earnings Per Share Targets | |||
| Compensation Plan [Line Items] | |||
| Restricted stock units earning per share, minimum |
0.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMinimum / us-gaap_VestingAxis = wti_RestrictedStockUnitsWithEarningPerSharePerformanceConditionsMember |
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| Restricted stock units earning per share, maximum |
100.00%wti_NumberOfRestrictedStockUnitsTargetAwardVestedRangeMaximum / us-gaap_VestingAxis = wti_RestrictedStockUnitsWithEarningPerSharePerformanceConditionsMember |
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| X | ||||||||||
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- Definition
Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Price of a single share of a number of saleable stocks of a company. No definition available.
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- Definition
Payment period after year end for annual incentive awards. No definition available.
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- Definition
Payment period after year end for cash-based awards. No definition available.
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- Details
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- Definition
Number of restricted stock units target award vested range maximum. No definition available.
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- Definition
Number of restricted stock units target award vested range minimum. No definition available.
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- Definition
Percentage of restricted stock units granted during period not subject to performance criteria. No definition available.
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions expected vesting month and year. No definition available.
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- Definition
The maximum performance period for share-based compensation awards made under the amended and restated compensation plan. No definition available.
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- Details
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