Annual report pursuant to Section 13 and 15(d)

Related Parties - Additional Information (Details)

v2.4.1.9
Related Parties - Additional Information (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Airplane Services      
Related Party Transaction [Line Items]      
Related party transactions $ 0.9us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_AirplaneServicesMember
$ 1.2us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_AirplaneServicesMember
$ 1.0us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_AirplaneServicesMember
Directional Drilling Services      
Related Party Transaction [Line Items]      
Related party transactions 0.2us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_DirectionalDrillingServicesMember
0.2us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_DirectionalDrillingServicesMember
0.7us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_DirectionalDrillingServicesMember
Minimum | Marine Transportation and Logistic Services      
Related Party Transaction [Line Items]      
Related party transactions $ 0.2us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_MarineTransportationAndLogisticsMember
$ 0.2us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_MarineTransportationAndLogisticsMember
$ 0.2us-gaap_RelatedPartyTransactionAmountsOfTransaction
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= wti_MarineTransportationAndLogisticsMember