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REVENUES FROM CONTRACT WITH CUSTOMERS (Details) - USD ($) $ in Millions | Jan. 31, 2021 | Jan. 31, 2020
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REVENUES FROM CONTRACT WITH CUSTOMERS |  |
Retained amounts by project owners | $ 36.8 | $ 20.0
Amounts of unpriced change orders included in transaction prices | 16.6 | 20.6

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- Definition Amounts of unpriced change orders included in transaction prices. + References No definition available. + Details
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Namespace Prefix: | agx_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

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