Significant accounting policies Accumulated other comprehensive loss (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity adjustment foreign currency	$ (268)	$ (1,409)
Minimum pension liability, gross	(1,307)	(1,472)
Marketable security, gross	0	142
Accumulated other comprehensive income before tax	(1,575)	(2,739)
Tax effect of foreign exchange	(6)	(50)
Tax effect of minimum pension liability	115	115
Tax effect of marketable security	0	(50)
Total accumulated other comprehensive loss	$ (1,466)	$ (2,724)