Significant accounting policies Cash and cash equivalents (Details) - USD ($) $ in Thousands	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 7,603	$ 16,631	$ 9,900
United States
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	200	200
Geographic Distribution, Foreign [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 7,400	$ 16,400