Income Taxes - Significant components of the company's deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Current deferred tax assets:
Accounts receivable	$ 184	$ 212
Inventories	664	978
Accrued vacation	647	887
Insurance obligations	137	383
Accrued benefit liabilities	0	41
Warranty obligations	262	565
Postretirement benefits	1,929	3,072
Uncertain tax positions	491	803
Share-based compensation	1,761	3,201
Other accrued liabilities	54	68
Deferred Tax Assets, Gross	6,129	10,210
Deferred tax(liabilities):
Depreciation and amortization	(6,082)	(10,565)
Deferred Tax Liabilities, Other	(643)	(1,048)
Deferred Tax Liabilities, Gross	6,725	11,613
Net Deferred Tax (Liability),	$ 596	$ 1,403