Document and Entity Information Document - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2020	Apr. 15, 2020
Cover [Abstract]
Document Type	10-K/A
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-15369
Entity Registrant Name	WILLIS LEASE FINANCE CORP
Entity Central Index Key	0001018164
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	68-0070656
Entity Address, Address Line One	4700 Lyons Technology Parkway
Entity Address, City or Town	Coconut Creek
Entity Address, State or Province	FL
Entity Address, Postal Zip Code	33073
City Area Code	561
Local Phone Number	349-9989
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	WLFC
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float		$ 76.6
Entity Common Stock, Shares Outstanding			6,749,008
Documents Incorporated by Reference	None.