Employee Retirement Benefits - The accumulated benefit obligation (Details) - Other Postretirement Benefit Plan, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 7,991	$ 12,125	$ 8,254
Service cost	80	285	195
Interest cost	333	386	366
Amendments	0	(958)	0
Actuarial loss (gain) and assumption changes	341	(3,544)	3,543
Retiree benefits paid	(329)	(303)	(233)
Benefit obligation at end of year	$ 8,416	$ 7,991	$ 12,125