QUARTERLY FINANCIAL INFORMATION (unaudited) (Details) - USD ($) $ in Millions	3 Months Ended
Jan. 31, 2019	Oct. 31, 2018
QUARTERLY FINANCIAL INFORMATION (unaudited)
Adjustment for research and development tax credit	$ 0.1	$ 16.5

The favourable adjustment recorded to recognize research and development tax credits in net income.

No definition available.

Name:	agx_AdjustmentForResearchAndDevelopmentTaxCreditRecognizeInNetIncome
Namespace Prefix:	agx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration