Summary of Significant Accounting Policies Foreign Currency - Devaluation (Details) $ in Millions	Dec. 31, 2018 USD ($)
Angola, Kwanza
Impact of Foreign Currency Devaluation [Line Items]
Net Monetary Asset Position	$ 28

[Line Items] for Impact of Foreign Currency Devaluation [Table]

No definition available.

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Namespace Prefix:	wft_
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Balance Type:	na
Period Type:	duration