Note 13 - Capital Stock - Summary of Stock Options Outstanding and Exercisable (Details) - $ / shares	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Options Outstanding Outstanding (in shares)	15,514,750	15,738,350	14,911,625	12,260,500
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.13	$ 1.30	$ 1.41	$ 1.33
Options Outstanding Weighted Average Remaining Contractual Term (Year)	5 years 233 days
Options Exercisable (in shares)	8,717,279
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.27
Options Exercisable Weighted Average Remaining Contractual Term (Year)	2 years 222 days
Exercise Price Range 1 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 0.80
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 0.99
Options Outstanding Outstanding (in shares)	8,169,500
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 0.92
Options Outstanding Weighted Average Remaining Contractual Term (Year)	7 years 233 days
Options Exercisable (in shares)	2,843,279
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 0.94
Options Exercisable Weighted Average Remaining Contractual Term (Year)	4 years 10 days
Exercise Price Range 2 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 1
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 1.49
Options Outstanding Outstanding (in shares)	5,005,000
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.19
Options Outstanding Weighted Average Remaining Contractual Term (Year)	3 years 295 days
Options Exercisable (in shares)	3,533,750
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.22
Options Exercisable Weighted Average Remaining Contractual Term (Year)	1 year 171 days
Exercise Price Range 3 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 1.50
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 3.28
Options Outstanding Outstanding (in shares)	2,340,250
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.75
Options Outstanding Weighted Average Remaining Contractual Term (Year)	2 years 215 days
Options Exercisable (in shares)	2,340,250
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.75
Options Exercisable Weighted Average Remaining Contractual Term (Year)	2 years 215 days