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Equity Structure and Transactions - Additional Information (Details) (USD $)
In Thousands, except Share data, unless otherwise specified |
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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| Equity Structure And Transactions [Line Items] | |||
| Preferred stock, shares authorized | 20,000,000us-gaap_PreferredStockSharesAuthorized | 20,000,000us-gaap_PreferredStockSharesAuthorized | |
| Preferred stock, par value | $ 0.00001us-gaap_PreferredStockParOrStatedValuePerShare | $ 0.00001us-gaap_PreferredStockParOrStatedValuePerShare | |
| Preferred stock, issued | 0us-gaap_PreferredStockSharesIssued | 0us-gaap_PreferredStockSharesIssued | |
| Cash dividends paid | $ 30,260us-gaap_PaymentsOfDividends | $ 58,846us-gaap_PaymentsOfDividends | $ 82,832us-gaap_PaymentsOfDividends |
| Common Stock, Regular | |||
| Equity Structure And Transactions [Line Items] | |||
| Paid cash dividends, per share |
$ 0.40us-gaap_CommonStockDividendsPerShareCashPaid / us-gaap_StatementClassOfStockAxis = wti_CommonStockRegularMember |
$ 0.36us-gaap_CommonStockDividendsPerShareCashPaid / us-gaap_StatementClassOfStockAxis = wti_CommonStockRegularMember |
$ 0.32us-gaap_CommonStockDividendsPerShareCashPaid / us-gaap_StatementClassOfStockAxis = wti_CommonStockRegularMember |
| Common Stock, Special | |||
| Equity Structure And Transactions [Line Items] | |||
| Paid cash dividends, per share |
$ 0.42us-gaap_CommonStockDividendsPerShareCashPaid / us-gaap_StatementClassOfStockAxis = wti_CommonStockSpecialMember |
$ 0.79us-gaap_CommonStockDividendsPerShareCashPaid / us-gaap_StatementClassOfStockAxis = wti_CommonStockSpecialMember |
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| Cash dividends paid |
$ 31,800us-gaap_PaymentsOfDividends / us-gaap_StatementClassOfStockAxis = wti_CommonStockSpecialMember |
$ 59,000us-gaap_PaymentsOfDividends / us-gaap_StatementClassOfStockAxis = wti_CommonStockSpecialMember |
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- Definition
Aggregate dividends paid during the period for each share of common stock outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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