The number of revenue categories.

No definition available.

Name:	agx_NumberOfCategories
Namespace Prefix:	agx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The value (monetary amount) of the award at the end of the contract the plaintiff could potentially seek in the legal matter.

+ References

No definition available.

+ Details

Name:	agx_PossibleLossContingencyDamagesSoughtValueEndOfContract
Namespace Prefix:	agx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the entity's revenue contributed to the parent entity as a percentage of the parent entity's total revenue.

+ References

No definition available.

+ Details

Name:	agx_RevenueContributedToParentAsPercentageOfTotalParentRevenue
Namespace Prefix:	agx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue recognition period.

+ References

No definition available.

+ Details

Name:	agx_RevenueRecognitionPeriod
Namespace Prefix:	agx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Schedule Of Description Of Business [Line Items]

+ References

No definition available.

+ Details

Name:	agx_ScheduleOfDescriptionOfBusinessLineItems
Namespace Prefix:	agx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The contract amount of unapproved change orders.

+ References

No definition available.

+ Details

Name:	agx_UnapprovedChangeOrdersContractAmount
Namespace Prefix:	agx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of revenue earned from products sold or services provided under the terms of a contract, including, but not limited to, government contracts and construction contracts, classified as other.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_ContractsRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=agx_PowerIndustryServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=agx_GemmaPowerSystemsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationStatusAxis=us-gaap_PendingLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationCaseAxis=agx_LiquidatedDamagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=agx_CoreServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=agx_ProjectDevelopmentServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION (Details) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Jun. 30, 2016 USD ($)	Jan. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Apr. 30, 2016 USD ($)	Jan. 31, 2016 USD ($)	Oct. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2017 USD ($) category	Jan. 31, 2016 USD ($)	Jan. 31, 2015 USD ($)
Description of the Business
Revenues		$ 206,760	$ 175,444	$ 162,495	$ 130,348	$ 116,386	$ 113,967	$ 97,434	$ 85,488	$ 675,047	$ 413,275	$ 383,110
Minimum
Description of the Business
Estimated useful lives of the assets										5 years
Maximum
Description of the Business
Estimated useful lives of the assets										39 years
Power industry services
Description of the Business
Unapproved change orders contract amount		$ 2,700								$ 2,700
Number of categories \| category										2
Revenues										$ 586,628	$ 387,636	$ 376,676
Power industry services \| Minimum
Description of the Business
Revenue recognition period										3 months
Power industry services \| Maximum
Description of the Business
Revenue recognition period										3 years
GPS
Description of the Business
Consolidated revenues by subsidiaries										85.00%	90.00%	98.00%
Pending Litigation \| Liquidated Damages
Description of the Business
Potential amount of damages sought by plaintiff at end of contract	$ 12,900
Core services \| Power industry services
Description of the Business
Revenues										$ 586,628	$ 383,378	$ 376,676
Project development success fees \| Power industry services
Description of the Business
Revenues											$ 4,258