Note 9 - Asset Retirement Obligations - Estimated Amounts and Timing of Cash Flows and Assumptions Used for ARO Estimates (Details) $ in Thousands	Jan. 31, 2024 USD ($)	Jul. 31, 2023 USD ($)
Undiscounted amount of estimated cash flows	$ 29,042	$ 29,064
Measurement Input, Expected Term [Member] | Minimum [Member]
Asset retirement obligations, measurement input	1	1
Measurement Input, Expected Term [Member] | Maximum [Member]
Asset retirement obligations, measurement input	23	23
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	0.0532
Measurement Input, Discount Rate [Member] | Minimum [Member]
Asset retirement obligations, measurement input	0.0372	0.0372
Measurement Input, Discount Rate [Member] | Maximum [Member]
Asset retirement obligations, measurement input	0.0635	0.0635