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REVENUES FROM CONTRACTS WITH CUSTOMERS (Details) - USD ($) $ in Millions | Oct. 31, 2019 | Jan. 31, 2019
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REVENUES FROM CONTRACTS WITH CUSTOMERS |  |
Retained amounts by project owners | $ 20.3 | $ 15.3

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- Definition The amounts retained by project owners under construction contracts. + References No definition available. + Details
Name: | agx_RetainedAmountUnderConstructionContracts
Namespace Prefix: | agx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration