Selected Balance Sheet Information (Details) - USD ($) $ in Thousands		Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Accounts receivable, net:
Trade accounts		$ 59,510	$ 43,834
Allowance for doubtful accounts		(978)	(691)
Accounts receivable, net		58,532	43,143
Inventories:
Finished goods		8,054	5,438
In process		961	2,288
Materials		46,336	34,610
Inventories		55,351	42,336
Other current assets:
Insurance policy benefit		759	802
Federal income taxes receivable		1,397	604
Prepaid expenses and other		3,705	1,283
Other current assets		5,861	2,689
Property, plant and equipment, net:
Property, plant and equipment, net		106,280	106,324
Other assets:
Equity investments		1,955	2,371
Deferred income taxes		19	18
Other		976	1,283
Other assets		2,950	3,672
Accrued liabilities:
Salaries and related		9,409	6,286
Benefits		4,225	3,960
Insurance obligations		1,992	2,400
Warranties		1,163	1,547	$ 1,835	$ 3,120
Accrued income taxes, current		226	498
Other taxes		1,880	1,540
Acquisition-related contingent liability, current		1,036	445
Other		2,015	1,379
Accrued liabilities		21,946	18,055
Other liabilities:
Postretirement benefits		8,264	8,054
Acquisition-related contingent consideration		2,010	1,397
Deferred income taxes		615	1,421
Uncertain tax positions		2,634	2,610
Other		272	214
Other liabilities		13,795	13,696
Land [Member]
Property, plant and equipment, net:
Property, plant and equipment, gross	[1]	3,234	3,054
Building and Improvements [Member]
Property, plant and equipment, net:
Property, plant and equipment, gross	[1]	80,299	77,817
Machinery and Equipment [Member]
Property, plant and equipment, net:
Property, plant and equipment, gross	[1]	149,847	142,471
Property, plant and equipment, Owned [Member]
Property, plant and equipment, net:
Accumulated amortization for capitalized leases	[1]	(127,523)	(117,018)
Property, plant and equipment, net	[1]	105,857	106,324
Assets Held under Capital Leases [Member]
Property, plant and equipment, net:
Machinery and equipment		488	0
Capital leases, lessee balance dheet, assets by major class, accumulated depreciation		(65)	0
Capital leases, balance sheet, assets by major class, net		423	0
Assets owned and held under capital lease [Member]
Property, plant and equipment, net:
Property, plant and equipment, net		$ 106,280	$ 106,324

[1] The amount of assets and liabilities held for sale as of January 31, 2018 are separately disclosed in Note 3 - Assets Held For Sale in Item 8 of this Form 10-K. There were no assets or liabilities held for sale as of January 31, 2017.