Employee Retirement Benefits - The liability and expense reflected in the balance sheet and income statement (Details) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Long-term portion in other liabilities	$ 8,741,000	$ 7,678,000
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	8,001,000	8,571,000
Net periodic benefit cost	297,000	312,000
Other comprehensive (gain) loss	1,116,000	(441,000)
Total recognized in net periodic benefit cost and other comprehensive income	1,413,000	(129,000)
Retiree benefits paid	341,000	441,000
Benefit obligation at end of year	9,073,000	8,001,000
Current portion in accrued liabilities	332,000	323,000
Long-term portion in other liabilities	$ 8,741,000	$ 7,678,000
Assumptions used to calculate benefit obligation:
Discount rate	3.14%	4.25%
Rate of compensation increase	4.00%	4.00%
Health care cost trend rate assumed for next year	6.17%	6.33%
Ultimate health care cost trend rate	4.50%	4.50%
Year that the rate reaches the ultimate trend rate	2030	2030
Assumptions used to calculate the net periodic benefit cost:
Discount rate	4.25%	3.75%
Rate of compensation increase	4.00%	4.00%
Defined Benefit Plan, Expected future payments
2021	$ 337,000
2022	344,000
2023	349,000
2024	350,000
2025	349,000
2026-2030	$ 1,864,000