Retirement plans 401K (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
401K employee pretax payroll contributions limit	16.00%
Employer contributions to 401K	$ 405	$ 558
Maximum % of each participant's salary	50.00%
Company's matching contribution	3.50%