Annual report pursuant to Section 13 and 15(d)

Consolidated Statement of Changes In Shareholders' Equity (Parenthetical)

v2.4.1.9
Consolidated Statement of Changes In Shareholders' Equity (Parenthetical) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Common Stock, Regular      
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      
Paid cash dividends, per share   $ 0.42us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_StatementClassOfStockAxis
= wti_CommonStockSpecialMember
$ 0.79us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_StatementClassOfStockAxis
= wti_CommonStockSpecialMember