Retirement plans Reconciliation of benefit obligations, plan assets and funded status (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Defined benefit plan vested benefit obligation	$ 6,500	$ 6,587
Defined Benefit Plan, Accumulated Benefit Obligation	6,500	7,020
Defined Benefit Plan, Benefit Obligation	6,500	7,020	$ 8,129
Interest cost	278	266
Actuarial (gain) loss	(493)	(1,115)
Benefits paid	(305)	(260)
Defined Benefit Plan, Fair Value of Plan Assets	6,228	5,883	$ 6,168
Defined Benefit Plan, actual gain (loss) on plan assets	650	(25)
Unfunded status	(272)	(1,137)
Defined benefit plan, current assets	348	326
Defined benefit plan, assets for plan benefits, other assets	1,201	1,166
Defined benefit plans, other long-term liabilities	(1,821)	(2,629)
Defined benefit plan, net amount recognized	(272)	(1,137)
OCI unrecognized actuarial loss	1,472	2,303
OCI net amount recognized	$ 1,472	$ 2,303