Employee Retirement Benefits - The liability and expense reflected in the balance sheet and income statement (Details) - USD ($)	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Long-term portion in other liabilities	$ 7,678,000	$ 8,264,000
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	8,571,000	8,416,000
Net periodic benefit cost	312,000	323,000
Other comprehensive (gain) loss	(441,000)	175,000
Total recognized in net periodic benefit cost and other comprehensive income	(129,000)	498,000
Retiree benefits paid	441,000	343,000
Benefit obligation at end of year	8,001,000	8,571,000
Current portion in accrued liabilities	323,000	307,000
Long-term portion in other liabilities	$ 7,678,000	$ 8,264,000
Assumptions used to calculate benefit obligation:
Discount rate	4.25%	3.75%
Rate of compensation increase	4.00%	4.00%
Health care cost trend rate assumed for next year	6.33%	6.50%
Ultimate health care cost trend rate	4.50%	4.50%
Year that the rate reaches the ultimate trend rate	2030	2030
Assumptions used to calculated the net periodic benefit cost:
Discount rate	3.75%	4.00%
Rate of compensation increase	4.00%	4.00%
Defined Benefit Plan, Expected future payments
2020	$ 330,000
2021	341,000
2022	349,000
2023	352,000
2024	354,000
2025-2029	$ 1,888,000