Summary of significant accounting policies (Details) - Net accounts receivable by segment - USD ($) $ in Thousands	Jul. 31, 2016	Jul. 31, 2015
Clinical Labs (by billing category)
Accounts Receivable Net Current	$ 14,592	$ 12,109
Clinical Labs [Member]
Clinical Labs (by billing category)
Accounts Receivable Net Current	$ 10,364	$ 8,194
Accounts Receivable Net Current Percentage	100.00%	100.00%
Life Sciences [Member]
Clinical Labs (by billing category)
Accounts Receivable Net Current	$ 4,228	$ 3,915
Third-Party Payor [Member] | Clinical Labs [Member]
Clinical Labs (by billing category)
Accounts Receivable Net Current	$ 6,868	$ 3,595
Accounts Receivable Net Current Percentage	67.00%	44.00%
Self-Pay [Member] | Clinical Labs [Member]
Clinical Labs (by billing category)
Accounts Receivable Net Current	$ 1,676	$ 3,213
Accounts Receivable Net Current Percentage	16.00%	39.00%
Medicare [Member] | Clinical Labs [Member]
Clinical Labs (by billing category)
Accounts Receivable Net Current	$ 1,486	$ 1,081
Accounts Receivable Net Current Percentage	14.00%	13.00%
Health Maintenance Organizations [Member] | Clinical Labs [Member]
Clinical Labs (by billing category)
Accounts Receivable Net Current	$ 334	$ 305
Accounts Receivable Net Current Percentage	3.00%	4.00%