Income Taxes Significant components of the company's deferred tax assets and liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Current deferred tax assets:
Accounts receivable	$ 58	$ 103	$ 103
Inventories	452	463	344
Accrued vacation	1,248	1,008	857
Insurance obligations	559	485	553
Warranty obligations	595	503	441
Other accrued liabilities	387	171	173
Deferred tax assets, net, current	3,299	2,733	2,471
Non-current deferred tax assets (liabilities):
Postretirement benefits	2,571	2,014	1,849
Depreciation and amortization	(9,673)	(3,050)	(1,970)
Uncertain tax positions	1,673	1,426	1,180
Other	911	534	521
Deferred tax liabilities, noncurrent	(4,518)	0	0
Deferred tax assets, net , noncurrent	0	924	1,580
Net deferred tax asset (liability)	$ (1,219)	$ 3,657	$ 4,051