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DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Jan. 31, 2020 | Jan. 31, 2021
Description of the Business |  |
Retained amounts by project owners | $ 20.0 | $ 36.8
Minimum |  |
Description of the Business |  |
Property, Plant and Equipment, Useful Life | 5 years |
Maximum |  |
Description of the Business |  |
Property, Plant and Equipment, Useful Life | 39 years |

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

X
- 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

X
- 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

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |