Earnings (Loss) Per Share Attributable to the Stockholders of Argan, Inc. - Additional Information (Detail) (USD $)	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Earnings Per Share [Abstract]
Additional shares included in the calculation of diluted EPS	356,000	330,000	180,000
Shares covered by antidilutive stock options	222,000	404,000	556,000
Income (loss) from continuing operations attributable to parent	$ 3,219,000	$ 1,448,000	$ 302,000