EARNINGS PER SHARE ATTRIBUTABLE TO THE STOCKHOLDERS OF ARGAN, INC. (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
EARNINGS PER SHARE ATTRIBUTABLE TO THE STOCKHOLDERS OF ARGAN, INC.
Net income attributable to the stockholders of Argan, Inc.	$ 17,229	$ 18,073	$ 64,993	$ 49,977
Weighted average number of shares outstanding - basic	15,545	15,137	15,509	14,974
Effect of stock options	248	464	287	516
Weighted average number of shares outstanding - diluted	15,793	15,601	15,796	15,490
Basic (in dollars per share)	$ 1.11	$ 1.19	$ 4.19	$ 3.34
Diluted (in dollars per share)	$ 1.09	$ 1.16	$ 4.11	$ 3.23