Selected Balance Sheet Information (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Accounts receivable, net:
Trade accounts	$ 54,962	$ 56,508	$ 60,929
Allowance for doubtful accounts	(319)	(205)	(170)
Accounts receivable, net	54,643	56,303	60,759
Inventories:
Finished goods	7,232	8,571	7,094
In process	2,131	2,675	6,105
Materials	45,502	34,943	41,557
Inventories	54,865	46,189	54,756
Other current assets:
Insurance policy benefit	733	860	1,873
Federal income taxes receivable	1,197	0	0
Prepaid expenses and other	1,358	936	1,030
Other current assets	3,288	1,796	2,903
Property, plant and equipment, net:
Accumulated depreciation	(84,624)	(75,420)	(67,054)
Property, plant and equipment, net	98,076	81,238	61,894
Other assets, net:
Investment in affiliate	3,684	4,063	4,409
Other, net	224	206	155
Other assets, net	3,908	4,269	4,564
Accrued liabilities:
Salaries and benefits	1,858	4,265	5,541
Vacation	3,700	4,025	4,387
401 (k) contributions	727	520	966
Insurance obligations	2,428	2,506	2,789
Warranties	2,525	1,888	1,699	1,437
Taxes - accrued and withheld	1,743	1,392	2,596
Acquisition-related contingent liability, current	890	712	3,266
Other	2,377	1,884	1,749
Accrued liabilities	16,248	17,192	22,993
Other liabilities:
Postretirement benefits	7,998	8,072	7,348
Acquisition-related contingent liability, noncurrent	2,457	2,359	7,655
Deferred income taxes	3,526	2,453	4,518
Uncertain tax positions	6,557	5,818	4,946
Other liabilities	20,538	18,702	24,467
Land [Member]
Property, plant and equipment, net:
Property, Plant and Equipment, Gross	2,077	2,077	2,077
Building and Improvements [Member]
Property, plant and equipment, net:
Property, Plant and Equipment, Gross	66,278	52,936	36,952
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, Plant and Equipment, Gross	$ 114,345	$ 101,645	$ 89,919