Goodwill and intangible assets (Details) - Schedule of intangible assets - USD ($) $ in Thousands	Jan. 31, 2018	Jul. 31, 2017
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	$ 27,738	$ 27,436
Finite-lived intangible assets, Accumulated Amortization	(25,289)	(24,541)
Finite-lived intangible assets, Net	2,449	2,895
Patents [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	11,027	11,027
Finite-lived intangible assets, Accumulated Amortization	(10,964)	(10,951)
Finite-lived intangible assets, Net	63	76
Customer Relationships [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	12,046	11,881
Finite-lived intangible assets, Accumulated Amortization	(9,667)	(9,083)
Finite-lived intangible assets, Net	2,379	2,798
Website And Acquired Content [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	1,022	1,011
Finite-lived intangible assets, Accumulated Amortization	(1,022)	(1,011)
Licensed Technology And Other [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	498	484
Finite-lived intangible assets, Accumulated Amortization	(491)	(463)
Finite-lived intangible assets, Net	7	21
Trademarks [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	3,145	3,033
Finite-lived intangible assets, Accumulated Amortization	$ (3,145)	$ (3,033)