Goodwill and intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended
Oct. 31, 2017	Jul. 31, 2017
Goodwill and intangible assets (Details) [Line Items]
Goodwill	$ 7,452	$ 7,452
Intangible Assets, Amortization Period [Member]
Goodwill and intangible assets (Details) [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years
Clinical Labs [Member]
Goodwill and intangible assets (Details) [Line Items]
Goodwill	$ 7,452	$ 7,452

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant