Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014
Accounts receivable, net:
Trade accounts	$ 40,370		$ 56,895	$ 52,797
Allowance for doubtful accounts	(481)		(319)	(344)
Accounts receivable, net	39,889		56,576	52,453
Inventories:
Finished goods	6,657		8,127	7,098
In process	3,957		1,317	1,694
Materials	43,452		45,708	42,464
Inventories	54,066		55,152	51,256
Other current assets:
Insurance policy benefit	637		733	876
Federal tax receivable	0		713	1,826
Receivable from sale of business	830		0	0
Prepaid Expense and other	2,341		1,648	3,049
Other current assets	3,808		3,094	5,751
Property, plant and equipment, net:
Property, plant and equipment, net	118,291		117,513	97,806
Other Assets, net (Noncurrent):
Investment in affiliate (equity method)	2,896		3,217	3,380
Other, net	1,243		526	478
Other assets, net	4,139		3,743	3,858
Accrued liabilities:
Salaries and related	2,031		4,063	2,115
Benefits	4,315		5,001	5,261
Insurance obligations	1,702		1,590	1,443
Warranties	1,752	$ 2,285	3,120	2,617	$ 2,654	$ 2,525
Income Taxes	1,108		536	133
Other taxes	1,031		1,240	983
Acquisition-related contingent consideration liability, Current	1,028		1,375	919
Other	1,082		2,262	1,805
Accrued liabilities	14,049		19,187	15,276
Other liabilities:
Postretirement benefits	12,151		11,812	8,166
Acquisition-related contingent consideration liability, Noncurrent	3,049		3,631	3,682
Deferred income taxes	5,764		7,091	2,172
Uncertain tax positions	3,280		3,259	7,118
Other liabilities	24,244		25,793	21,138
Land [Member]
Property, plant and equipment, net:
Property, plant and equipment	324		11	0
Building and Building Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment	2,597		1,522	0
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment	639		0	0
Assets Held-for-sale [Member]
Property, plant and equipment, net:
Accumulated depreciation	(2,207)		(627)	0
Property, plant and equipment, net	1,353		906	0
Land [Member]
Property, plant and equipment, net:
Property, plant and equipment	2,921		3,246	2,077
Building and Building Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment	76,697		78,140	68,439
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment	136,666		131,766	118,833
Assets held for use [Member]
Property, plant and equipment, net:
Accumulated depreciation	(99,346)		(96,545)	(91,543)
Property, plant and equipment, net	116,938		116,607	97,806
Assets held for use [Member] | Assets Held-for-sale [Member]
Property, plant and equipment, net:
Property, plant and equipment, net	$ 118,291		$ 117,513	$ 97,806