Note 12 - Asset Retirement Obligations - Estimated Amounts and Timing of Cash Flows and Assumptions Used for ARO Estimates (Details)	Jul. 31, 2022	Jul. 31, 2021
Measurement Input, Expected Term [Member] | Minimum [Member]
Asset retirement obligations, measurement input	1	9
Measurement Input, Expected Term [Member] | Maximum [Member]
Asset retirement obligations, measurement input	23	21
Measurement Input, Inflation Rate [Member] | Minimum [Member]
Asset retirement obligations, measurement input	0.0156	0.0156
Measurement Input, Inflation Rate [Member] | Maximum [Member]
Asset retirement obligations, measurement input	0.0532	0.0217
Measurement Input, Discount Rate [Member] | Minimum [Member]
Asset retirement obligations, measurement input	0.0372	0.0550
Measurement Input, Discount Rate [Member] | Maximum [Member]
Asset retirement obligations, measurement input	0.0635	0.0596