Derivative Financial Instruments - Cash Receipts on Derivative Settlements, Net Included within Net Cash Provided by Operating Activities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Cash receipts on derivative settlements, net	$ 713	$ 4,105

Cash proceeds payments on derivative settlements net operating activities.

No definition available.

Name:	wti_CashProceedsPaymentsOnDerivativeSettlementsNetOperatingActivities
Namespace Prefix:	wti_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration