(LOSS) INCOME 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, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
(LOSS) INCOME PER SHARE ATTRIBUTABLE TO THE STOCKHOLDERS OF ARGAN, INC.
Net (loss) income attributable to the stockholders of Argan, Inc.	$ (7,188)	$ (6,855)	$ 1,154	$ (29,800)	$ (2,207)	$ 32,434	$ 16,972	$ 4,837	$ (42,689)	$ 52,036	$ 72,011
Weighted average number of shares outstanding - basic									15,621	15,569	15,522
Effects of stock awards										124	258
Weighted average number of shares outstanding - diluted									15,621	15,693	15,780
Basic (in Dollars per share)	$ (0.46)	$ (0.44)	$ 0.07	$ (1.91)	$ (0.14)	$ 2.08	$ 1.09	$ 0.31	$ (2.73)	$ 3.34	$ 4.64
Diluted (in Dollars per share)	$ (0.46)	$ (0.44)	$ 0.07	$ (1.91)	$ (0.14)	$ 2.07	$ 1.08	$ 0.31	$ (2.73)	$ 3.32	$ 4.56