Goodwill and intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2015	Jul. 31, 2015
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	4 years