Note 13 - Stock-based Compensation - Schedule of Outstanding Stock Options (Details) - $ / shares	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Balance, number of stock options (in shares)	14,911,625	12,260,500	12,105,858
Balance, Weighted Average Exercise Price (in dollars per share)	$ 1.41	$ 1.33	$ 1.34
Granted, number of stock options (in shares)	2,006,350	4,083,000	672,500
Granted, Weighted Average Exercise Price (in dollars per share)	$ 0.97	$ 1.40	$ 1.11
Exercised, number of stock options (in shares)	(259,625)	(1,365,625)	(412,134)
Exercised Options, Weighted Average Exercise Price (in dollars per share)	$ 1.12	$ 0.70	$ 0.56
Expired, number of stock options (in shares)	(10,000)		(100,724)
Expired, Weighted Average Exercise Price (in dollars per share)	$ 1.50		$ 4.35
Forfeited, number of stock options (in shares)	(910,000)	(66,250)	(5,000)
Forfeited, Weighted Average Exercise Price (in dollars per share)	$ 2.41	$ 1.24	$ 0.93
Balance, number of stock options (in shares)	15,738,350	14,911,625	12,260,500
Balance, Weighted Average Exercise Price (in dollars per share)	$ 1.30	$ 1.41	$ 1.33