Organization and Summary of Significant Accounting Policies - Investments and Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Equity ownership of the venture	50.00%
Amortization of initial direct costs associated with leases	$ 0.9	$ 0.7

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