Selected Balance Sheet Information (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Accounts receivable, net:
Accounts receivable, net	$ 56,303	$ 60,759	$ 39,967
Inventories:
Finished goods	8,571	7,094	7,994
In process	2,675	6,105	5,424
Materials	34,943	41,557	30,261
Inventories	46,189	54,756	43,679
Other current assets:
Insurance policy benefit	860	1,873	1,909
Prepaid expenses and other	936	1,030	1,330
Other current assets	1,796	2,903	3,239
Property, plant and equipment, net:
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(75,420)	(67,054)	(60,558)
Property, plant and equipment, net	81,238	61,894	41,522
Other assets, net:
Investment in affiliate	4,063	4,409	4,728
Deferred income taxes	0	0	924
Other, net	206	155	43
Other assets, net	4,269	4,564	5,695
Accrued liabilities:
Salaries and benefits	3,978	4,297	3,264
Vacation	4,025	4,387	3,186
401 (k) contributions	520	966	253
Insurance obligations	2,506	2,789	3,356
Profit sharing	287	1,244	1,627
Warranties	1,888	1,699	1,437	1,259
Taxes - accrued and withheld	1,392	2,596	1,453
Acquisition-related contingent consideration	712	3,266	263
Other	1,884	1,749	1,257
Accrued liabilities	17,192	22,993	16,096
Other liabilities:
Postretirement benefits	8,072	7,348	5,757
Acquisition-related contingent consideration	2,359	7,655	2,230
Deferred income taxes	2,453	4,518	0
Uncertain tax positions	5,818	4,946	4,224
Other liabilities	18,702	24,467	12,211
Trade accounts [Member]
Accounts receivable, net:
Trade accounts	56,508	60,929	40,267
Allowance for doubtful accounts	(205)	(170)	(300)
Accounts receivable, net	56,303	60,759	39,967
Land [Member]
Property, plant and equipment, net:
Property, Plant and Equipment, Gross	2,077	2,077	1,798
Building and improvements [Member]
Property, plant and equipment, net:
Property, Plant and Equipment, Gross	52,936	36,952	24,972
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, Plant and Equipment, Gross	$ 101,645	$ 89,919	$ 75,310