Income Taxes - Significant components of the company's deferred tax assets and liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Current deferred tax assets:
Accounts receivable	$ 194	$ 111	$ 70
Inventories	873	583	507
Accrued vacation	940	1,032	1,118
Insurance obligations	271	276	302
Accrued benefit liabilities	261	291	274
Warranty obligations	1,225	898	661
Other accrued liabilities	194	181	175
Deferred tax assets, net, current	3,958	3,372	3,107
Non-current deferred tax assets (liabilities):
Postretirement benefits	4,243	2,799	2,826
Depreciation and amortization	(16,099)	(11,522)	(9,114)
Uncertain tax positions	1,002	2,219	1,969
Share-based compensation	2,897	2,309	1,613
Other	866	669	253
Net deferred tax liability	(7,091)	(3,526)	(2,453)
Deferred Tax Liabilities, Net	(3,133)	(154)
Net deferred tax (liability) asset			$ 654