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CONSTRUCTION JOINT VENTURES (Details) - GPS	6 Months Ended
	Jul. 31, 2017 item project
Variable Interest Entity
Number of natural gas-fired power plants | project	2
Number of joint ventures | item	2

X

- Definition

Represents the number of natural gas-fired power plants for which the entity has assigned its contracts for engineering, procurement and construction.

+ References

No definition available.

+ Details

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

X

- Definition

Number of joint venture under contract with company.

+ References

No definition available.

+ Details

Name:	agx_NumberOfJointVentureUnderContractWithCompany
Namespace Prefix:	agx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_VariableInterestEntityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

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