Goodwill and intangible assets (Details) - Schedule of intangible assets (USD $) In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	$ 28,478	$ 28,214
Finite-lived intangible assets, Accumulated Amortization	(20,370)	(18,271)
Finite-lived intangible assets, Net	8,108	9,943
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	(10,775)	(10,587)
Finite-lived intangible assets, Net	252	440
Customer Relationships [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	12,602	12,446
Finite-lived intangible assets, Accumulated Amortization	(6,565)	(5,448)
Finite-lived intangible assets, Net	6,037	6,998
Website And Acquired Content [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	1,037	1,026
Finite-lived intangible assets, Accumulated Amortization	(1,037)	(980)
Finite-lived intangible assets, Net		46
Licensed Technology And Other [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	537	513
Finite-lived intangible assets, Accumulated Amortization	(434)	(382)
Finite-lived intangible assets, Net	103	131
Trademarks [Member]
Goodwill and intangible assets (Details) - Schedule of intangible assets [Line Items]
Finite-lived intangible assets, Gross	3,275	3,202
Finite-lived intangible assets, Accumulated Amortization	(1,559)	(874)
Finite-lived intangible assets, Net	$ 1,716	$ 2,328