Retirement plans Reconciliation of benefit obligations, plan assets and funded status of plan (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Reconciliation of benefit obligations, plan assets and funded status of plan [Abstract]
Defined benefit plan vested benefit obligation	$ 6,650	$ 6,576
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	2,479	2,945
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Transition Assets (Obligations), before Tax	113	(1,380)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Gains (Losses), before Tax	303	(1)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	50	127
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	466	(1,254)
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	300
Defined Benefit Plan, Accumulated Benefit Obligation	7,240		7,186
Defined Benefit Plan, Amortization of Net Prior Service Cost (Credit)	50
Accumulated benefits	7,240	7,186	5,570
Fair value of plan assets	6,065	5,502	5,089
Defined Benefit Plan, Actual Return on Plan Assets	574	342
Service cost	171	126	126
Interest cost	299	313	313
Actuarial (gain) loss	(113)	1,380
Benefits paid	(303)	(203)
Company contributions	292	274
Unfunded status	(1,175)	(1,684)
Defined Benefit Plan, Current Assets	328	305
Defined Benefit Plan, Assets for Plan Benefits, Noncurrent	1,304	1,261
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	(2,807)	(3,250)
Defined Benefit Plan, Contributions by Plan Participants	0
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	328
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	337
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	351
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	356
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	380
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	1,989
Defined Benefit Plan, Amounts Recognized in Balance Sheet	(1,175)	(1,684)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	2,206	2,623
Unamortized prior service cost	$ 273	$ 322