Name:	us-gaap_AssetsFairValueDisclosureNonrecurring
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

No definition available.

Name:	us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Nonrecurring impairment charges related to the write-off of production-related equipment and inventory. This tag is used when an Entity charges this cost to cost of goods sold.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_ProductionRelatedImpairmentsOrCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Additional Production Related Impairments Or Charges

No definition available.

Name:	wlfc_AdditionalProductionRelatedImpairmentsOrCharges
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Equipment Held For Lease

No definition available.

Name:	wlfc_EquipmentHeldForLease
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Equipment held for sale.

No definition available.

Name:	wlfc_EquipmentHeldForSale
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

Name:	wlfc_FairValueAssetsAndGainLossesMeasuredOnNonrecurringBasisLineItems
Namespace Prefix:	wlfc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Gain Loss On Equipment Held For Lease

No definition available.

Name:	wlfc_GainLossOnEquipmentHeldForLease
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of gain (loss) in equipment held for sale recorded during the period.

No definition available.

Name:	wlfc_GainLossOnEquipmentHeldForSale
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Gain Loss On Spare Parts Inventory

No definition available.

Name:	wlfc_GainLossOnSparePartsInventory
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of Engines

No definition available.

Name:	wlfc_NumberOfEngines
Namespace Prefix:	wlfc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the number of engines for which impairment is recorded earlier due to a management decision to consign six engines for part-out and sale.

No definition available.

Name:	wlfc_NumberOfEnginesImpairmentRecordedEarlierDueToPartOutAndSale
Namespace Prefix:	wlfc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Spare Parts Inventory

No definition available.

Name:	wlfc_SparePartsInventory
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_EquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=wlfc_EnginePartsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=wlfc_EngineAndAircraftMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: