Document Entity and Information - shares	3 Months Ended
	Sep. 30, 2020	Nov. 05, 2020
Document Entity Information
Document Type	10-Q
Entity Interactive Data Current	Yes
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Registrant Name	General Finance CORP
Entity Central Index Key	0001342287
Current Fiscal Year End Date	--06-30
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Common Stock, Shares Outstanding		30,175,225
Entity Address, State or Province	CA
Document Quarterly Report	true
Document Transition Report	false
Entity Emerging Growth Company	false
Entity Address, Address Line One	39 East Union Street
Entity File Number	001-32845
Entity Incorporation, State or Country Code	DE
Entity Address, City or Town	Pasadena
Entity Address, Postal Zip Code	91103
Entity Tax Identification Number	32-0163571
City Area Code	626
Local Phone Number	584-9722
Common Stock
Document Entity Information
Trading Symbol	GFN
Title of 12(b) Security	Common Stock, $0.0001 par value
Security Exchange Name	NASDAQ
Series C Cumulative Redeemable Perpetual Preferred Stock
Document Entity Information
Trading Symbol	GFNCP
Title of 12(b) Security	9.00% Series C Cumulative Redeemable Perpetual Preferred Stock (Liquidation Preference $100 per share)
Security Exchange Name	NASDAQ
Senior Notes Due
Document Entity Information
Trading Symbol	GFNSL
Title of 12(b) Security	8.125% Senior Notes due 2021
Security Exchange Name	NASDAQ