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DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jul. 31, 2016 | Jul. 31, 2016 | Jul. 31, 2015
Power Industry Services |  |  |
Description of the Business |  |  |
Unapproved change orders contract amount | $ 4.0 | $ 4.0 |
Outstanding litigation settled amount | $ 12.9 |  |
Power Industry Services | Minimum |  |  |
Description of the Business |  |  |
Revenue recognition period |  | 3 months |
Power Industry Services | Maximum |  |  |
Description of the Business |  |  |
Revenue recognition period |  | 3 years |
GPS |  |  |
Description of the Business |  |  |
Consolidated revenues by subsidiaries |  | 84.00% | 95.00%

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- Definition Reflects the estimated amount of loss from the specified contingency that was settled during the report period. + References No definition available. + Details
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Namespace Prefix: | agx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents the entity's revenue contributed to the parent entity as a percentage of the parent entity's total revenue. + References No definition available. + Details
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Namespace Prefix: | agx_
Data Type: | num:percentItemType
Balance Type: | na
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- Definition Revenue recognition period. + References No definition available. + Details
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Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Schedule Of Description Of Business [Line Items] + References No definition available. + Details
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Namespace Prefix: | agx_
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Balance Type: | na
Period Type: | duration

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- Definition The contract amount of unapproved change orders. + References No definition available. + Details
Name: | agx_UnapprovedChangeOrdersContractAmount
Namespace Prefix: | agx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=agx_PowerIndustryServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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