Employee Retirement Benefits - The accumulated benefit obligation (Details) - Other Postretirement Benefit Plan, Defined Benefit $ in Thousands	12 Months Ended
	Jan. 31, 2020 USD ($) basesppoints	Jan. 31, 2019 USD ($) ReportingUnits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 8,001	$ 8,571
Service cost	27	28
Interest cost	333	316
Actuarial (gain) loss and assumption changes	1,053	(473)
Retiree benefits paid	341	441
Benefit obligation at end of year	9,073	$ 8,001
Plan assets on unfunded plan	$ 0
Defined benefit plan change in discount rate	111	50
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change	$ 400