Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016
Accounts receivable, net:
Trade accounts	$ 47,350		$ 43,834	$ 39,203
Allowance for doubtful accounts	(952)		(691)	(558)
Accounts receivable, net	46,398		43,143	38,645
Inventories:
Finished goods	5,878		5,438	4,784
In process	1,510		2,288	1,929
Materials	43,456		34,610	38,789
Inventories	50,844		42,336	45,502
Other current assets:
Insurance policy benefit	734		802	762
Income tax receivable	409		604	1,652
Receivable from sale of business	35		28	103
Prepaid Expense and other	2,492		1,255	2,441
Other current assets	3,670		2,689	4,958
Property, plant and equipment, net:
Property, plant and equipment, net	105,723		106,324	110,706
Other Assets (Noncurrent):
Equity investments	2,057		2,371	2,611
Deferred Tax Assets, Net, Noncurrent	16		18	38
Other	1,222		1,283	1,134
Other assets	3,295		3,672	3,783
Accrued liabilities:
Salaries and related	5,138		6,286	3,628
Benefits	3,868		3,960	3,632
Insurance obligations	2,492		2,400	1,975
Warranties	2,265	$ 2,405	1,547	2,076	$ 2,316	$ 1,835
Income Taxes	1,287		498	213
Other taxes	1,503		1,540	1,357
Acquisition-related contingent consideration liability, Current	478		445	381
Other	1,693		1,379	823
Accrued liabilities	18,724		18,055	14,085
Other liabilities:
Postretirement benefits	8,085		8,054	7,706
Acquisition-related contingent consideration liability, Noncurrent	1,182		1,397	1,565
Deferred income taxes	488		1,421	1,557
Uncertain tax positions	2,593		2,610	2,999
Liabilities, Noncurrent	0		214	0
Other liabilities	12,348		13,696	13,827
Land [Member]
Property, plant and equipment, net:
Property, plant and equipment	3,234		3,054	3,054
Building and Building Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment	79,648		77,817	78,310
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment	145,516		142,471	142,185
Assets held for use [Member]
Property, plant and equipment, net:
Accumulated depreciation	(122,675)		(117,018)	(112,843)
Property, plant and equipment, net	$ 105,723		$ 106,324	$ 110,706