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=6880815&loc=d3e20235-122688

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

The amount of property, by major property class, net of accumulated depreciation, subject to or available for lease as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6454179&loc=d3e41551-112718

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph b(i)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 19

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseNet
Namespace Prefix:	us-gaap_
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

- Details

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

Represents the amount of gain (loss) in equipment held for operating lease recorded during the period.

No definition available.

Name:	wlfc_GainLossOnEquipmentHeldForOperatingLease
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.