QUARTERLY FINANCIAL INFORMATION (unaudited) - Schedule of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
QUARTERLY FINANCIAL INFORMATION (Unaudited)
Revenues	$ 116,386	$ 113,967	$ 97,434	$ 85,488	$ 102,325	$ 127,564	$ 102,030	$ 51,191	$ 413,275	$ 383,110	$ 227,455
Gross profit	23,543	26,262	28,493	21,167	21,675	30,313	21,564	10,051	99,465	83,603	78,848
Income from operations	14,461	20,672	23,645	15,627	15,538	24,840	17,083	6,672	74,405	64,133	65,930
Net income	9,160	14,359	15,834	10,851	9,876	16,759	12,020	4,800	50,204	43,455	43,344
Net income attributable to the stockholders of Argan, Inc.	$ 6,728	$ 10,807	$ 11,307	$ 7,503	$ 5,998	$ 12,422	$ 8,550	$ 3,475	$ 36,345	$ 30,445	$ 40,125
Earnings per share
Basic (in Dollars per share)	$ 0.45	$ 0.73	$ 0.77	$ 0.51	$ 0.41	$ 0.86	$ 0.59	$ 0.24	$ 2.46	$ 2.11	$ 2.85
Diluted (in Dollars per share)	$ 0.45	$ 0.72	$ 0.75	$ 0.50	$ 0.40	$ 0.84	$ 0.58	$ 0.24	$ 2.42	$ 2.05	$ 2.78