Summary of significant accounting policies (Details) - Segment's net revenues and revenue percentages (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Summary of significant accounting policies (Details) - Segment's net revenues and revenue percentages [Line Items]
Sales Revenue Services Net	$ 58,689	$ 55,889	$ 59,403
Clinical Labs [Member] | Third-Party Payor [Member]
Summary of significant accounting policies (Details) - Segment's net revenues and revenue percentages [Line Items]
Sales Revenue Services Net	29,509	26,014	29,616
Sales Revenue Services Net Percentage	50.00%	47.00%	50.00%
Clinical Labs [Member] | Medicare [Member]
Summary of significant accounting policies (Details) - Segment's net revenues and revenue percentages [Line Items]
Sales Revenue Services Net	12,815	12,497	12,658
Sales Revenue Services Net Percentage	22.00%	22.00%	21.00%
Clinical Labs [Member] | Self-Pay [Member]
Summary of significant accounting policies (Details) - Segment's net revenues and revenue percentages [Line Items]
Sales Revenue Services Net	11,204	12,172	11,895
Sales Revenue Services Net Percentage	19.00%	22.00%	20.00%
Clinical Labs [Member] | Health Maintenance Organizations [Member]
Summary of significant accounting policies (Details) - Segment's net revenues and revenue percentages [Line Items]
Sales Revenue Services Net	5,161	5,206	5,234
Sales Revenue Services Net Percentage	9.00%	9.00%	9.00%
Clinical Labs [Member]
Summary of significant accounting policies (Details) - Segment's net revenues and revenue percentages [Line Items]
Sales Revenue Services Net	$ 58,689	$ 55,889	$ 59,403
Sales Revenue Services Net Percentage	100.00%	100.00%	100.00%