Note 14 - Stock-based Compensation - Summary of Stock Options Outstanding and Exercisable (Details) - $ / shares	12 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2019
Options Outstanding Outstanding (in shares)	10,404,333	15,514,750	15,738,350
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.21	$ 1.13	$ 1.30
Options Outstanding Weighted Average Remaining Contractual Term (Year)	6 years 317 days
Options Exercisable (in shares)	6,513,126
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.16
Options Exercisable Weighted Average Remaining Contractual Term (Year)	5 years 178 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)	5,342,620
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 0.92
Options Outstanding Weighted Average Remaining Contractual Term (Year)	8 years 204 days
Options Exercisable (in shares)	3,289,024
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 0.92
Options Exercisable Weighted Average Remaining Contractual Term (Year)	8 years 127 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)	2,500,125
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.17
Options Outstanding Weighted Average Remaining Contractual Term (Year)	5 years 109 days
Options Exercisable (in shares)	1,616,791
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.21
Options Exercisable Weighted Average Remaining Contractual Term (Year)	3 years 109 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)	$ 2.80
Options Outstanding Outstanding (in shares)	2,561,588
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.84
Options Outstanding Weighted Average Remaining Contractual Term (Year)	4 years 317 days
Options Exercisable (in shares)	1,607,311
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.61
Options Exercisable Weighted Average Remaining Contractual Term (Year)	1 year 313 days