Document and Entity Information - shares	9 Months Ended
	Oct. 31, 2017	Dec. 01, 2017
Document And Entity Information
Entity Registrant Name	ARGAN INC
Entity Central Index Key	0000100591
Trading Symbol	AGX
Document Type	10-Q
Document Period End Date	Oct. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--01-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		15,548,719
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3