Name:	us-gaap_AssetManagementFees1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Carrying amount as of the balance sheet date of obligations due all related parties.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(3),(4))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.17)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_DueToRelatedPartiesCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

Represents the number of engines sold by the entity.

No definition available.

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

The amount Number of shares repurchased

No definition available.

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

Represents the amount of cash inflow from sale of engines.

No definition available.

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

The price of the stock at the close of the period.

No definition available.

Name:	wlfc_StockRepurchasedDuringPeriodClosingPricePerShare
Namespace Prefix:	wlfc_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The differential percentage between stock repurchase and closing price.

No definition available.

Name:	wlfc_StockRepurchasedDuringPeriodDifferentialPercentBetweenPurchaseAndClosingPrice
Namespace Prefix:	wlfc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The price at which the shares are bought back by the entity.

No definition available.

Name:	wlfc_StockRepurchasedDuringPeriodPurchasePricePerShare
Namespace Prefix:	wlfc_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=wlfc_WillisMitsuiAndCompanyEngineSupportLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_OtherIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=wlfc_CSCWillisEngineLeaseCompanyLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_ChiefExecutiveOfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: