Summary of significant accounting policies (Details) $ in Thousands	12 Months Ended
	Jul. 31, 2016 USD ($) shares	Jul. 31, 2015 USD ($) shares	Jul. 31, 2014 USD ($) shares	Jul. 31, 2013 USD ($)
Summary of significant accounting policies (Details) [Line Items]
Number of Operating Segments	3
Cash and Cash Equivalents, at Carrying Value	$ 67,777	$ 18,109	$ 17,455	$ 9,007
Contractual Adjustment Percentage	84.00%	85.00%	86.00%
Minimum Collection Period for Outstanding Accounts Receivable	210 days	210 days
Percentage Of Account Receivable Over Specified Days	100.00%	100.00%
Maximum Period for Allowance for Doubtful Accounts	210 days	210 days
Percentage of Doubtful Accounts to Accounts Receivable	19.40%	12.90%
Finite-Lived Intangible Asset, Useful Life	10 years
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 0	$ 0
Advertising Expense	$ 601	556	440
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in Shares) | shares	449,000
Share-based Compensation	$ 525	429	594
Excess Tax Benefit from Share-based Compensation, Operating Activities	0	$ 0	$ 0
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 810
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	16 months
Outstanding Options [Member]
Summary of significant accounting policies (Details) [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in Shares) | shares	282,000	977,000	182,000
Foreign Bank [Member]
Summary of significant accounting policies (Details) [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 500	$ 500
Clinical Labs [Member]
Summary of significant accounting policies (Details) [Line Items]
Sales Revenue Services Net Percentage	100.00%	100.00%	100.00%
Receivable Percentage	71.00%	68.00%
Life Sciences [Member]
Summary of significant accounting policies (Details) [Line Items]
Royalties Receivable	$ 500	$ 100
Minimum [Member]
Summary of significant accounting policies (Details) [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years
Minimum [Member] | Building and Building Improvements [Member]
Summary of significant accounting policies (Details) [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	15
Minimum [Member] | Machinery and Equipment [Member]
Summary of significant accounting policies (Details) [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	3
Maximum [Member]
Summary of significant accounting policies (Details) [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Maximum [Member] | Building and Building Improvements [Member]
Summary of significant accounting policies (Details) [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	30
Maximum [Member] | Machinery and Equipment [Member]
Summary of significant accounting policies (Details) [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	10
In the Money Stock Options [Member] | Unvested Restricted Stock [Member]
Summary of significant accounting policies (Details) [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in Shares) | shares		403,000	1,016,000
United Health Care of New York [Member] | Clinical Labs [Member]
Summary of significant accounting policies (Details) [Line Items]
Sales Revenue Services Net Percentage	30.00%	28.00%	25.00%