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Description of the Business and Basis of Presentation - Additional Information (Detail) (GPS [Member], Revenue [Member])
3 Months Ended
Apr. 30, 2015
Apr. 30, 2014
GPS [Member] | Revenue [Member]
   
Schedule Of Description Of Business [Line Items]    
Consolidated revenues by subsidiaries 97.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ dei_LegalEntityAxis
= agx_GemmaPowerSystemsMember
97.30%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ dei_LegalEntityAxis
= agx_GemmaPowerSystemsMember