PURCHASE OF ATLANTIC PROJECTS COMPANY LIMITED - Proforma information (Details 4) - Atlantic Projects Company Limited [Member] - USD ($)	3 Months Ended	6 Months Ended
Jul. 31, 2015	Jul. 31, 2015	Jul. 31, 2014
Business Acquisition, Pro Forma Information [Abstract]
Adjustment to net income for amortization of purchased intangibles		$ 43,000	$ (91,000)
acquisition related costs		457,000
Revenue since acquisition	$ 3,415,000	3,415,000
Income before income taxes since acquisition	150,000	150,000
Revenues from overseas customers since acquisition	$ 2,961,000	2,961,000
Pro forma revenues		192,505	173,214
Pro forma net income		27,891	17,594
Pro forma net income attributable to the stockholders of Argan, Inc.		$ 20,016	$ 12,798
Earnings Per Share, Pro Forma [Abstract]
Basic		$ 1.36	$ 0.89
Diluted		$ 1.33	$ 0.87

Business acquisitions pro forma profit loss.

No definition available.

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- Definition

This element represents the amount of earnings or loss before taxes of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

No definition available.

+ Details

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- Definition

This element represents the amount of revenue from overseas customers of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

No definition available.

+ Details

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- Definition

The element represents the increase (decrease) in net income related to adjustment for amortization of purchased intangibles.

+ References

No definition available.

+ Details

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- Definition

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460

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- Definition

This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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