Notes Receivable (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012 aircraft engine lessee item
Notes Receivable
Number of notes receivable relating to settlement agreements	1
Notes receivable	$ 0.7
Number of lessees with notes receivable	1
Number of aircraft leased	2
Number of engines leased	1
Notes receivable due in April 2016
Notes Receivable
Notes receivable	$ 1.0
Notes receivable term	5 years
Interest rate of notes receivable (as a percent)	5.00%

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Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10(3))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Subparagraph 3

-Article 9

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the number of lessees from which notes are receivable to the entity.

+ References

No definition available.

+ Details

Name:	wlfc_NotesReceivableFromNumberOfLessees
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the stated interest rate of notes receivable.

+ References

No definition available.

+ Details

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

- Definition

Represents the term for notes receivable under the agreement.

+ References

No definition available.

+ Details

Name:	wlfc_NotesReceivableTerm
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Data Type:	xbrli:durationItemType
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- Definition

Represents the number of aircraft leased by the entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of engines leased by the entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of notes receivable relating to settlement agreements at the end of the period.

+ References

No definition available.

+ Details

Name:	wlfc_NumberOfNotesReceivableRelatingToSettlementAgreements
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