Income Taxes - Significant components of the company's deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2019	Jan. 31, 2018
Current deferred tax assets:
Accounts receivable	$ 147	$ 184
Inventories	1,110	664
Accrued vacation	695	647
Insurance obligations	187	137
Warranty obligations	200	262
Postretirement benefits	1,800	1,929
Uncertain tax positions	487	491
Share-based compensation	1,834	1,761
Other accrued liabilities	913	54
Deferred Tax Assets, Gross	7,373	6,129
Deferred tax(liabilities):
Depreciation and amortization	(8,498)	(6,082)
Deferred Tax Liabilities, Other	(518)	(643)
Deferred Tax Liabilities, Gross	(9,016)	(6,725)
Net Deferred Tax (Liability),	$ (1,643)	$ (596)