Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Oct. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Apr. 30, 2015	Jan. 31, 2015
Accounts receivable, net:
Trade accounts	$ 40,257		$ 39,103	$ 40,062
Allowance for doubtful accounts	(703)		(1,034)	(769)
Accounts receivable, net	39,554		38,069	39,293
Inventories:
Finished goods	5,686		4,896	5,211
In process	2,325		1,845	2,157
Materials	34,802		39,098	41,268
Inventories	42,813		45,839	48,636
Other current assets:
Insurance policy benefit	776		716	728
Federal tax receivable	228		1,721	0
Receivable from sale of business	71		255	420
Prepaid Expense and other	1,672		1,737	1,767
Other current assets	2,747		4,429	2,915
Property, plant and equipment, net:
Accumulated Impairment, Property, Plant and Equipment			(554)	(554)
Property, plant and equipment, net	108,948		115,704	117,206
Other Assets (Noncurrent):
Equity investments	2,346		2,805	2,720
Deferred Tax Assets, Net, Noncurrent	65		0	0
Other	1,335		1,322	1,139
Other assets	3,746		4,127	3,859
Accrued liabilities:
Salaries and related	3,931		1,883	1,177
Benefits	3,720		3,864	3,925
Insurance obligations	2,022		1,730	1,852
Warranties	1,852	$ 2,076	1,835	1,639	$ 1,752	$ 3,120
Income Taxes	332		475	748
Other taxes	1,230		1,117	977
Acquisition-related contingent consideration liability, Current	396		407	448
Other	1,225		731	831
Accrued liabilities	14,708		12,042	11,597
Other liabilities:
Postretirement benefits	7,714		7,662	7,898
Acquisition-related contingent consideration liability, Noncurrent	1,385		1,732	1,483
Deferred income taxes	257		3,247	2,205
Uncertain tax positions	2,778		2,999	2,925
Other liabilities	12,134		15,640	14,511
Land [Member]
Property, plant and equipment, net:
Property, plant and equipment	0		244	324
Building and Building Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment	0		1,595	2,597
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment	0		329	639
Assets Held-for-sale [Member]
Property, plant and equipment, net:
Accumulated depreciation	0		(1,368)	(2,207)
Property, plant and equipment, net	0		800	1,353
Land [Member]
Property, plant and equipment, net:
Property, plant and equipment	3,054		3,054	2,974
Building and Building Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment	78,703		77,827	76,775
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment	143,533		140,996	138,921
Assets held for use [Member]
Property, plant and equipment, net:
Accumulated depreciation	(115,726)		(106,419)	(102,263)
Accumulated Impairment, Property, Plant and Equipment	(616)
Property, plant and equipment, net	108,948		114,904	115,853
Assets held for use [Member] | Assets Held-for-sale [Member]
Property, plant and equipment, net:
Property, plant and equipment, net	$ 108,948		$ 115,704	$ 117,206