Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017
Accounts receivable, net:
Trade accounts	$ 59,138		$ 57,063
Unbilled receivables	3,167		2,447
Allowance for doubtful accounts	(957)		(978)
Accounts receivable, net	61,348		58,532
Inventories:
Finished goods	6,709		8,054
In process	1,406		961
Materials	47,878		46,336
Inventories	55,993		55,351
Other current assets:
Insurance policy benefit	714		759
Income tax receivable	16		1,397
Receivable from sale of investments	1,055		0
Prepaid Expense and other	3,587		3,705
Other current assets	5,372		5,861
Property, plant and equipment, net:
Property, plant and equipment, net	106,716		106,280
Other Assets (Noncurrent):
Equity investments	175		1,955
Deferred Income Taxes, Noncurrent	20		19
Other	2,642		976
Other assets	2,837		2,950
Accrued liabilities:
Salaries and related	5,759		9,409
Benefits	4,045		4,225
Insurance obligations	2,488		1,992
Warranties	1,137	$ 1,097	1,163	$ 2,265	$ 2,405	$ 1,547
Income Taxes	1,667		226
Other taxes	1,357		1,880
Acquisition-related contingent consideration liability, current	1,709		1,036
Other	3,713		2,015
Accrued liabilities	21,875		21,946
Other liabilities:
Postretirement benefits	8,260		8,264
Acquisition-related contingent consideration liability, long-term	1,241		2,010
Deferred income taxes	168		615
Uncertain tax positions	2,636		2,634
Other Liabilities, Noncurrent	4,010		272
Other liabilities	16,315		13,795
Land [Member]
Property, plant and equipment, net:
Property, plant and equipment	3,234		3,234
Building and Building Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment	81,092		80,299
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment	155,515		149,847
Property, plant and equipment, Owned [Member]
Property, plant and equipment, net:
Accumulated depreciation	(133,482)		(127,523)
Property, plant and equipment, net	106,359		105,857
Assets Held under Capital Leases [Member]
Property, plant and equipment, net:
Property, plant and equipment	510		488
Accumulated depreciation	(153)		(65)
Assets owned or held under capital lease [Member]
Property, plant and equipment, net:
Property, plant and equipment, net	$ 106,716		$ 106,280