Stockholders' equity (Tables)

12 Months Ended

Jul. 31, 2020

Stockholders' Equity Note [Abstract]

Schedule of share-based payment award, stock options, valuation assumptions

	2020					2019					2018
	Options			Weighted - Average Exercise Price		Options			Weighted - Average Exercise Price		Options			Weighted - Average Exercise Price
Outstanding at beginning of year		2,351,040		$	4.53		1,882,116		$	4.96		2,132,995		$	4.26
New Grants		773,032		$	2.40		715,321		$	2.81		415,580		$	5.57
Exercised		—		$	—		(238,230	)	$	2.69		(635,624	)	$	2.98
Expired or forfeited		(487,576	)	$	3.71		(8,167	)	$	6.55		(30,835	)	$	5.97
Outstanding at end of year		2,636,496		$	4.05		2,351,040		$	4.53		1,882,116		$	4.99
Exercisable at end of year		1,457,162		$	5.10		1,342,564		$	5.16		1,149,489		$	4.28
Weighted average fair value of options granted during year				$	1.01				$	1.07				$	1.91

Schedule of share based compensation stock options activity range of exercise prices

Grant Year	Options Granted	Exercise Price Range	Term (years)	Vesting Period (years)	FMV of options Granted/Per Share	Expected Life (years)	Expected Volatility %	Interest Rate %	Vested Shares at 7/31/2020
2020	773,032	$2.20 - $3.32	5	2 - 3	$0.86 - $1.34	3.25 – 3.5	53.77 – 66.24	0.27 – 1.2	—
2019	715,321	$2.80 - $3.21	5	2 - 3	$1.06 – $1.23	3.25 - 3.5	48.06 - 50.56	2.47- 2.96	359,411
2018	415,580	$4.42 - $8.36	5	2 - 3	$1.53 - $2.76	3.25 - 3.5	42.59 - 46.14	2.07- 2.79	247,150

Schedule of share based compensation stock options activity range of exercise prices

Range of Exercise prices	Shares		Weighted-Average Remaining Contractual Life in Years	Weighted-Average Exercise Price
$2.20 - $3.32		1,389,245	2.5	$	2.58
$4.35 - $4.66		696,705	1.5	$	4.46
$5.52 - $8.36		550,546	2.0	$	7.26
		2,636,496

Range of Exercise prices	Shares		Weighted-Average Remaining Contractual Life in Years	Weighted-Average Exercise Price
$2.20 - $3.32		359,411	3.4	$	2.80
$4.35 - $4.66		558,372	1.5	$	4.47
$5.52 - $8.36		539,379	2.0	$	7.28
		1,457,162

Schedule of nonvested performance-based units activity

Grant Date	Total Grant		Forfeitures			Outstanding		Fair Market Value At Grant Date (000s)
7/31/2018		32,000		(4,000	)		28,000	$	124
1/3/2019		80,500		(10,500	)		70,000	$	196
2/25/2020		98,600		—			98,600	$	217