Note 12 - Stock-based Compensation - Summary of Stock Options Outstanding and Exercisable (Details)	6 Months Ended
	Jan. 31, 2019 $ / shares shares
Options Outstanding Outstanding (in shares) | shares	14,703,125
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.41
Options Outstanding Weighted Average Remaining Contractual Term (Year)	2 years
Options Exercisable (in shares) | shares	12,290,625
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.41
Options Exercisable Weighted Average Remaining Contractual Term (Year)	1 year 211 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)	$ 1.30
Options Outstanding Outstanding (in shares) | shares	5,086,625
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.11
Options Outstanding Weighted Average Remaining Contractual Term (Year)	2 years 266 days
Options Exercisable (in shares) | shares	4,177,125
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.08
Options Exercisable Weighted Average Remaining Contractual Term (Year)	2 years 193 days
Exercise Price Range 2 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 1.31
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 3.86
Options Outstanding Outstanding (in shares) | shares	9,616,500
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.57
Options Outstanding Weighted Average Remaining Contractual Term (Year)	1 year 226 days
Options Exercisable (in shares) | shares	8,113,500
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.58
Options Exercisable Weighted Average Remaining Contractual Term (Year)	1 year 32 days