DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION (Policies)	3 Months Ended
	Apr. 30, 2017
DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION
Description of the Business	Description of the Business The condensed consolidated financial statements include the accounts of Argan, Inc. (“Argan”), its wholly owned subsidiaries, its majority-controlled joint ventures and any variable interest entities for which Argan or one of its wholly-owned subsidiaries is deemed to be the primary beneficiary. Argan conducts operations through its wholly owned subsidiaries, Gemma Power Systems, LLC and affiliates (“GPS”), which provided 90% and 79% of consolidated revenues for the three months ended April 30, 2017 and 2016, respectively; The Roberts Company, Inc. (“TRC”); Atlantic Projects Company Limited and affiliates (“APC”) and Southern Maryland Cable, Inc. (“SMC”). Argan and these consolidated subsidiaries are hereinafter cumulatively referred to as the “Company.” Through GPS and APC, the Company provides a full range of engineering, procurement, construction, commissioning, operations management, maintenance, development, technical and consulting services to the power generation and renewable energy markets for a wide range of customers, including independent power project owners, public utilities, power plant equipment suppliers and global energy plant construction firms. GPS, including its consolidated joint ventures and variable interest entities, and APC represent our power industry services reportable segment. Through TRC, the industrial fabrication and field services reportable segment provides on-site services that support maintenance turnarounds, shutdowns and emergency mobilizations for industrial plants primarily located in the southern United States and that are based on its expertise in producing, delivering and installing fabricated steel components such as pressure vessels, heat exchangers and piping systems. Through SMC, the telecommunications infrastructure services segment provides project management, construction, installation and maintenance services to commercial, local government and federal government customers primarily in the mid-Atlantic region.
Basis of Presentation	Basis of Presentation In Note 14, the Company has provided certain financial information relating to the operating results and assets of its reportable segments based on the manner in which management disaggregates the Company’s financial reporting for purposes of making internal operating decisions. All significant inter-company balances and transactions have been eliminated in consolidation. The deferred tax amounts included in the comparative balance sheet were reclassified to conform to the current year presentation. The Company’s fiscal year ends on January 31 of each year. These condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and note disclosures normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“US GAAP”) have been condensed or omitted pursuant to those rules and regulations, although the Company believes that the disclosures made are adequate to make the information not misleading. The accompanying condensed consolidated financial statements and notes should be read in conjunction with the consolidated financial statements, the notes thereto (including the summary of significant accounting policies), and the independent registered public accounting firm’s report thereon that are included in the Company’s Annual Report on Form 10-K for the fiscal year ended January 31, 2017. The condensed consolidated balance sheet as of April 30, 2017, the condensed consolidated statements of earnings for the three months ended April 30, 2017 and 2016, and the condensed consolidated statements of cash flows for the three months ended April 30, 2017 and 2016 are unaudited. The condensed consolidated balance sheet as of January 31, 2017 has been derived from audited financial statements. In the opinion of management, the accompanying condensed consolidated financial statements contain all adjustments, which are of a normal and recurring nature, considered necessary to present fairly the financial position of the Company as of April 30, 2017, and its earnings and cash flows for the interim periods presented. The results of operations for any interim period are not necessarily indicative of the results of operations for any other interim period or for a full fiscal year.
Revenue Recognition	Revenue Recognition — Revenues are recognized primarily under various long-term construction contracts, including contracts for which revenues are based on either a fixed price, cost-plus-fee or time and materials basis, with typical durations of one month to three years. Revenues from fixed price construction contracts, including a portion of estimated profit, are recognized as services are provided, based on costs incurred and estimated total contract costs using the percentage of completion method. Revenues from cost-plus-fee construction contracts are recognized on the basis of costs incurred during the period plus the amount of fee earned. Revenues from time and materials contracts are recognized when the related services are provided to the customer. Changes to total estimated contract costs or losses, if any, are recognized in the period in which they are determined.
Fair Values	Fair Values — The carrying value amounts presented in the condensed consolidated balance sheets for the Company’s cash and cash equivalents, short-term investments, accounts receivable and accounts payable are reasonable estimates of their fair values due to the short-term nature of these instruments. The fair value amounts of reporting units (as needed for purposes of identifying indications of impairment to goodwill) are determined by averaging valuations that are calculated using several market-based and income-based approaches deemed appropriate in the circumstances.