Name:	us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

Name:	us-gaap_OperatingLeasesIncomeStatementAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The amount of expense recognized in the current period that reflects the allocation of capitalized costs associated with acquisition of leases.

No definition available.

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

Amount represents the value of maintenance right assets at the end of the reporting period.

No definition available.

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

maintenance rights

No definition available.