Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015
Accounts receivable, net:
Trade accounts	$ 39,203		$ 39,103	$ 40,370
Allowance for doubtful accounts	(558)		(1,034)	(481)
Accounts receivable, net	38,645		38,069	39,889
Inventories:
Finished goods	4,784		4,896	6,657
In process	1,929		1,845	3,957
Materials	38,789		39,098	43,452
Inventories	45,502		45,839	54,066
Other current assets:
Insurance policy benefit	762		716	637
Federal tax receivable	1,652		1,721	0
Receivable from sale of business	103		255	830
Prepaid Expense and other	2,441		1,737	2,341
Other current assets	4,958		4,429	3,808
Property, plant and equipment, net:
Property, plant and equipment, net	110,706		115,704	118,291
Other Assets (Noncurrent):
Equity investments	2,611		2,805	2,896
Deferred Tax Assets, Net, Noncurrent	38		0	0
Other	1,134		1,322	1,243
Other assets	3,783		4,127	4,139
Accrued liabilities:
Salaries and related	3,628		1,883	2,031
Benefits	3,632		3,864	4,315
Insurance obligations	1,975		1,730	1,702
Warranties	2,076	$ 2,316	1,835	1,752	$ 2,285	$ 3,120
Income Taxes	213		475	1,108
Other taxes	1,357		1,117	1,031
Acquisition-related contingent consideration liability, Current	381		407	1,028
Other	823		731	1,082
Accrued liabilities	14,085		12,042	14,049
Other liabilities:
Postretirement benefits	7,706		7,662	12,151
Acquisition-related contingent consideration liability, Noncurrent	1,565		1,732	3,049
Deferred income taxes	1,557		3,247	5,764
Uncertain tax positions	2,999		2,999	3,280
Other liabilities	13,827		15,640	24,244
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	2,921
Building and Building Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment	78,340		77,827	76,697
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment	142,709		140,996	136,666
Assets held for use [Member]
Property, plant and equipment, net:
Accumulated depreciation	(112,843)		(106,419)	(99,346)
Accumulated Impairment, Property, Plant and Equipment	(554)		(554)	0
Property, plant and equipment, net	110,706		114,904	116,938
Assets held for use [Member] | Assets Held-for-sale [Member]
Property, plant and equipment, net:
Property, plant and equipment, net	$ 110,706		$ 115,704	$ 118,291