EARNINGS PER SHARE ATTRIBUTABLE TO THE STOCKHOLDERS OF ARGAN, INC. (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
EARNINGS PER SHARE ATTRIBUTABLE TO THE STOCKHOLDERS OF ARGAN, INC.
Net income attributable to the stockholders of Argan, Inc.	$ (2,207)	$ 32,434	$ 16,972	$ 4,837	$ 7,018	$ 17,229	$ 27,139	$ 20,625	$ 52,036	$ 72,011	$ 70,328
Weighted average number of shares outstanding - basic									15,569	15,522	15,066
Effect of stock awards									124	258	559
Weighted average number of shares outstanding - diluted									15,693	15,780	15,625
Basic (in Dollars per share)	$ (0.14)	$ 2.08	$ 1.09	$ 0.31	$ 0.45	$ 1.11	$ 1.75	$ 1.33	$ 3.34	$ 4.64	$ 4.67
Diluted (in Dollars per share)	$ (0.14)	$ 2.07	$ 1.08	$ 0.31	$ 0.45	$ 1.09	$ 1.72	$ 1.31	$ 3.32	$ 4.56	$ 4.50