Employee Retirement Benefits - The accumulated benefit obligation (Details) - Other Postretirement Benefit Plan, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 8,416	$ 7,991
Service cost	74	80
Interest cost	312	333
Actuarial loss (gain) and assumption changes	112	341
Retiree benefits paid	343	329
Benefit obligation at end of year	$ 8,571	$ 8,416