Income Taxes - Significant components of the company's deferred tax assets and liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Current deferred tax assets:
Accounts receivable	$ 111	$ 70	$ 58
Inventories	583	507	452
Accrued vacation	1,032	1,118	1,248
Insurance obligations	567	576	559
Warranty obligations	898	661	595
Other accrued liabilities	181	175	387
Deferred tax assets, net, current	3,372	3,107	3,299
Non-current deferred tax assets (liabilities):
Postretirement benefits	2,799	2,826	2,571
Depreciation and amortization	(11,522)	(9,114)	(9,673)
Uncertain tax positions	2,219	1,969	1,673
Share-based compensation	2,309	1,613	981
Other	669	253	(70)
Net deferred tax liability	(3,526)	(2,453)	(4,518)
Net deferred tax (liability) asset	$ (154)	$ 654	$ (1,219)