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Organization and Summary of Significant Accounting Policies (Details 3) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Equipment Held for Operating Lease      
Impairment charge $ 5,602us-gaap_ProductionRelatedImpairmentsOrCharges $ 6,461us-gaap_ProductionRelatedImpairmentsOrCharges $ 5,874us-gaap_ProductionRelatedImpairmentsOrCharges
Minimum      
Equipment Held for Operating Lease      
Estimated useful life 3 years    
Maximum      
Equipment Held for Operating Lease      
Estimated useful life 5 years    
Engines and aircraft      
Equipment Held for Operating Lease      
Impairment charge $ 2,400us-gaap_ProductionRelatedImpairmentsOrCharges
/ us-gaap_MajorPropertyClassAxis
= wlfc_EnginesAndAircraftMember		 $ 0us-gaap_ProductionRelatedImpairmentsOrCharges
/ us-gaap_MajorPropertyClassAxis
= wlfc_EnginesAndAircraftMember		 $ 0us-gaap_ProductionRelatedImpairmentsOrCharges
/ us-gaap_MajorPropertyClassAxis
= wlfc_EnginesAndAircraftMember
Equipment held for lease Member | Engines and related equipment      
Equipment Held for Operating Lease      
Estimated useful life 15 years    
Residual value (as a percent) 55.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
/ us-gaap_MajorPropertyClassAxis
= wlfc_EnginesAndRelatedEquipmentMember
/ us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis
= us-gaap_PropertyAvailableForOperatingLeaseMember		    
Equipment held for lease Member | Spare part packages      
Equipment Held for Operating Lease      
Residual value (as a percent) 25.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
/ us-gaap_MajorPropertyClassAxis
= wlfc_SparePartPackagesMember
/ us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis
= us-gaap_PropertyAvailableForOperatingLeaseMember		    
Equipment held for lease Member | Spare part packages | Minimum      
Equipment Held for Operating Lease      
Estimated useful life 14 years    
Equipment held for lease Member | Spare part packages | Maximum      
Equipment Held for Operating Lease      
Estimated useful life 15 years    
Equipment held for lease Member | Aircraft | Minimum      
Equipment Held for Operating Lease      
Estimated useful life 13 years    
Residual value (as a percent) 15.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
/ us-gaap_MajorPropertyClassAxis
= wlfc_AircraftMember
/ us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis
= us-gaap_PropertyAvailableForOperatingLeaseMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		    
Equipment held for lease Member | Aircraft | Maximum      
Equipment Held for Operating Lease      
Estimated useful life 20 years    
Residual value (as a percent) 17.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
/ us-gaap_MajorPropertyClassAxis
= wlfc_AircraftMember
/ us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis
= us-gaap_PropertyAvailableForOperatingLeaseMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember