Supplemental Guarantor Information - Additional Information (Details)	Dec. 31, 2016
Debt Disclosure [Abstract]
Percentage of subsidiaries owned	100.00%

Parent's ownership percentage of certain subsidiaries.

No definition available.

Name:	wti_PercentageOfSubsidiaryOwnedByParent
Namespace Prefix:	wti_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant