Net income (loss) per share (Details) - shares	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
In the Money Stock Options [Member]
Net income (loss) per share (Details) [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	888,000		888,000
Unvested Restricted Stock [Member]
Net income (loss) per share (Details) [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	804,000		804,000
Weighted Average Stock Options [Member]
Net income (loss) per share (Details) [Line Items]
Antidilutive Securities Included In Computation Of Earnings Per Share Amount	440,000		281,000
Outstanding Options [Member]
Net income (loss) per share (Details) [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	494,000	235,000	247,000	305,000