Organization and Summary of Significant Accounting Policies - Intangibles and Other Assets (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Other Assets [Abstract]
Prepaid Deposits	$ 10,500,000	$ 10,600,000
Customer Relationships
Intangible Assets
Useful life	5 years
Indefinite-lived Intangible Assets
Intangible Assets
Intangible assets with indefinite useful lives	$ 0

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

+ Details

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

- Definition

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.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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Period Type:	instant

- References

No definition available.

+ Details

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- Definition

Amount of asset related to consideration paid in advance for deposits.

+ References

No definition available.

+ Details

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

- Details

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- Details

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