Income Taxes - Significant components of the company's deferred tax assets and liabilities (Details) - USD ($) $ in Thousands		Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Current deferred tax assets:
Accounts receivable	[1]	$ 212	$ 355	$ 194
Inventories	[1]	978	602	873
Accrued vacation	[1]	887	836	940
Insurance obligations	[1]	383	350	271
Accrued benefit liabilities	[1]	41	99	261
Warranty obligations	[1]	565	670	1,225
Postretirement benefits		3,072	2,797	4,243
Uncertain tax positions		803	896	1,002
Share-based compensation		3,201	3,613	4,410
Other accrued liabilities	[1]	68	198	194
Deferred Tax Assets, Gross		10,210	10,416	13,613
Deferred tax(liabilities):
Depreciation and amortization		(10,565)	(9,886)	(16,099)
Deferred Tax Liabilities, Other		(1,048)	(667)	(647)
Deferred Tax Liabilities, Gross		11,613	10,553	16,746
Net Deferred Tax (Liability),		$ 1,403	$ 137	$ 3,133

[1] As discussed below, under the prior accounting guidance these deferred tax assets were classified as current deferred tax assets. All other deferred tax assets and liabilities were classified as non-current.