Significant accounting policies Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016
Goodwill [Line Items]
Goodwill description	allocated between intangible assets and the net tangible assets of the acquired business with the residual of the purchase price recorded as goodwill
Goodwill, Acquired During Period	$ 2,279
Goodwill	$ 2,279	$ 0
Date of annual goodwill impairment test	impairment assessment of goodwill annually as of January 31
No goodwill impairment	There was no impairment to goodwill