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SPECIAL PURPOSE ENTITIES - Additional Information (Details) - GPS $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 2015 USD ($) | Jan. 31, 2016 item project
Variable Interest Entity |  |
Number of natural gas-fired power plants | project |  | 2
Number of joint ventures | item |  | 2
Cash distributions to joint venture partner | $ | $ 25 |

X
- Definition The cash distribution made by the joint venture to the joint venture partner other then the reporting entity. + References No definition available. + Details
Name: | agx_JointVentureCashDistributionToJointVenturePartner
Namespace Prefix: | agx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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: |