Supplemental Oil and Gas Disclosures - Cost Incurred in Oil and Gas Property Acquisition Exploration and Development Activities (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capitalized Costs Oil And Gas Producing Activities Net [Abstract]
Additions of asset retirement obligations	$ 20.3	$ 21.3	$ 10.8
Seismic costs	1.5	0.5	0.2
Geological and geophysical costs	$ 5.4	$ 4.2	$ 4.1

Geological and Geophysical costs incurred related to development and exploration of oil and gas properties. These costs are included in operating expenses, and therefore are an adjustment to derive costs related to the acquisition of oil and gas properties.

No definition available.

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