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Share-Based and Cash-Based Incentive Compensation - Additional Information (Details) (USD $)
In Millions, except Share data, unless otherwise specified |
12 Months Ended | 3 Months Ended | 12 Months Ended | |
|---|---|---|---|---|
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Dec. 31, 2014
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Mar. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Common stock available for award under plans | 4,790,082us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant | |||
| Additional shares authorized under share based compensation arrangements | 4,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized | |||
| Common Stock | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Unrecognized share-based compensation expense |
0.1us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember |
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| Recognition period for unrecognized compensation expense | 2015-02 | |||
| Chief Executive Officer | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Number of shares granted |
42,547us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_TitleOfIndividualAxis = us-gaap_ChiefExecutiveOfficerMember |
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| Number of shares issued |
42,547us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod / us-gaap_TitleOfIndividualAxis = us-gaap_ChiefExecutiveOfficerMember |
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| Directors Compensation Plan | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Common stock available for award under plans |
500,564us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant / us-gaap_AwardTypeAxis = wti_DirectorsCompensationPlanMember |
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| Restricted Shares | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Shares granted, grant date fair value |
0.3wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
0.3wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
0.4wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
|
| Shares vested, vested date fair value |
0.3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
0.4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
0.5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
|
| Number of shares granted |
18,815us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
27,450us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
21,954us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Unrecognized share-based compensation expense |
0.5us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
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| Recognition period for unrecognized compensation expense | 2017-04 | |||
| Restricted Stock Units (RSUs) | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Shares granted, grant date fair value |
20.1wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
12.8wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
14.3wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
|
| Shares vested, vested date fair value |
2.0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
7.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
20.0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
|
| Expected volatility, minimum |
30.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
33.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| Expected volatility, maximum |
63.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
74.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| Adjusted EBITDA |
40.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAdjustedEBITDA / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| Adjusted EBITDA margin |
30.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAdjustedEBITDAMargin / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| TSR ranking |
30.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsTSRRanking / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
30.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsTSRRanking / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| TSR ranking for each of three-year performance periods |
10.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsTSRRankingEachYear / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
10.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsTSRRankingEachYear / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| EPS comprised |
70.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsEPSComprised / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| Number of shares granted |
1,195,388us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
969,919us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
764,654us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
|
| Unrecognized share-based compensation expense |
16.5us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| Recognition period for unrecognized compensation expense | 2016-11 | |||
| Restricted Stock Units (RSUs) | London Interbank Offered Rate (LIBOR) | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Risk-free interest rate, minimum |
0.27%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_VariableRateAxis = us-gaap_LondonInterbankOfferedRateLIBORMember |
0.15%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_VariableRateAxis = us-gaap_LondonInterbankOfferedRateLIBORMember |
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| Risk-free interest rate, maximum |
0.91%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_VariableRateAxis = us-gaap_LondonInterbankOfferedRateLIBORMember |
0.72%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_VariableRateAxis = us-gaap_LondonInterbankOfferedRateLIBORMember |
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| Restricted Stock Units (RSUs) | Minimum | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Expected dividend yield |
0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
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| Correlation of movement of total shareholder return |
(84.00%)wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsCorrelationOfReturns / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
(67.00%)wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsCorrelationOfReturns / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
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| Restricted Stock Units (RSUs) | Maximum | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Expected dividend yield |
3.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
2.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
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| Correlation of movement of total shareholder return |
95.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsCorrelationOfReturns / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
94.00%wti_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsCorrelationOfReturns / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
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- Definition
Unrecognized cost of unvested share-based compensation awards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. No definition available.
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- Definition
The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. No definition available.
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| X | ||||||||||
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- Definition
The maximum risk-free interest rate assumption that is used in valuing an option on its own shares. No definition available.
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- Definition
The minimum risk-free interest rate assumption that is used in valuing an option on its own shares. No definition available.
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- Details
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- Definition
Number of additional shares authorized for issuance under an established share-based compensation plan. No definition available.
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- Definition
The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Number of share instruments newly issued under a share-based compensation plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The grant date fair value of share-based compensation arrangements (other than options) granted in the period. No definition available.
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions adjusted EBITDA. No definition available.
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions adjusted EBITDA margin. No definition available.
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions correlation of returns. No definition available.
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions EPS comprised. No definition available.
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions TSR ranking total. No definition available.
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions TSR ranking each year. No definition available.
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- Definition
Share based compensation arrangement by share based payment award unrecognized compensation expenses period for recognition. No definition available.
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