Retirement plans Cash flows (Details) $ in Thousands	12 Months Ended
	Jan. 31, 2017 USD ($)
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year	$ 0
Defined Benefit Plan, Contributions by Plan Participants	0
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	348
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	345
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	347
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	342
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	347
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	$ 1,733