Employee Retirement Benefits - The accumulated benefit obligation (Details) - Other Postretirement Benefit Plan, Defined Benefit $ in Thousands	12 Months Ended
	Jan. 31, 2021 USD ($) basesppoints	Jan. 31, 2020 USD ($) basesppoints
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 9,073	$ 8,001
Service cost	36	27
Interest cost	280	333
Actuarial loss and assumption changes	303	1,053
Retiree benefits paid	(332)	(341)
Benefit obligation at end of year	9,360	$ 9,073
Plan assets on unfunded plan	$ 0
Defined benefit plan change in discount rate | basesppoints	24	111
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change	$ 31	$ 400