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, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
EARNINGS PER SHARE ATTRIBUTABLE TO THE STOCKHOLDERS OF ARGAN, INC.
Net income attributable to the stockholders of Argan, Inc.	$ 20,351	$ 18,073	$ 19,674	$ 12,230	$ 6,728	$ 10,807	$ 11,307	$ 7,503	$ 70,328	$ 36,345	$ 30,445
Weighted average number of shares outstanding - basic									15,066	14,757	14,433
Effect of stock options									559	267	390
Weighted average number of shares outstanding - diluted									15,625	15,024	14,823
Basic (in Dollars per share)	$ 1.33	$ 1.19	$ 1.32	$ 0.82	$ 0.45	$ 0.73	$ 0.77	$ 0.51	$ 4.67	$ 2.46	$ 2.11
Diluted (in Dollars per share)	$ 1.29	$ 1.16	$ 1.29	$ 0.81	$ 0.45	$ 0.72	$ 0.75	$ 0.50	$ 4.50	$ 2.42	$ 2.05