Document and Entity Information - USD ($)	12 Months Ended
	Jan. 31, 2017	Apr. 07, 2017	Jul. 31, 2016
Document And Entity Information
Entity Registrant Name	ARGAN INC
Entity Central Index Key	0000100591
Trading Symbol	AGX
Document Type	10-K
Document Period End Date	Jan. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--01-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		15,465,719
Entity Public Float			$ 513,266,000
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY