Note 12 - Stock-based Compensation - Summary of Stock Options Outstanding and Exercisable (Details) - $ / shares	9 Months Ended
	Apr. 30, 2019	Jul. 31, 2018
Range of Exercise Prices, Lower Limit (in dollars per share)
Range of Exercise Prices, Upper Limit (in dollars per share)
Options Outstanding Outstanding (in shares)	14,736,375	14,911,625
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.41	$ 1.41
Options Outstanding Weighted Average Remaining Contractual Term (Year)	1 year 277 days
Options Exercisable (in shares)	12,756,125
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.40
Options Exercisable Weighted Average Remaining Contractual Term (Year)	1 year 146 days
Exercise Price Range 1 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 0.93
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 1.41
Options Outstanding Outstanding (in shares)	11,384,875
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.23
Options Outstanding Weighted Average Remaining Contractual Term (Year)	1 year 120 days
Options Exercisable (in shares)	10,942,625
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.23
Options Exercisable Weighted Average Remaining Contractual Term (Year)	1 year 91 days
Exercise Price Range 2 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 1.42
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 3.86
Options Outstanding Outstanding (in shares)	3,351,500
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 2.04
Options Outstanding Weighted Average Remaining Contractual Term (Year)	3 years 83 days
Options Exercisable (in shares)	1,813,500
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 2.48
Options Exercisable Weighted Average Remaining Contractual Term (Year)	2 years 131 days