SEGMENT INFORMATION (Details)		3 Months Ended								12 Months Ended
		Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) reportable_segment product Rate	Dec. 31, 2016 USD ($) reportable_segment	Dec. 31, 2015 USD ($)
Industry segment and foreign operations
Number of reportable business segments | reportable_segment										2	2
Number of primary product groups | product										2
Financial results of reportable segments
Sales		$ 90,175,000	$ 84,991,000	$ 78,197,000	$ 64,557,000	$ 86,794,000	$ 67,211,000	$ 70,186,000	$ 67,822,000	$ 317,920,000	$ 292,013,000	$ 315,249,000
Depreciation and amortization										8,905,000	8,789,000	8,824,000
Segment (loss) income										8,934,000	3,395,000	4,937,000
Capital expenditures										3,207,000	2,479,000	4,210,000
Segment assets		318,949,000				297,550,000				318,949,000	297,550,000	310,938,000
Reconciliation of segment income to consolidated income before income taxes
Income from continuing operations before income taxes										$ 8,683,000	3,067,000	4,438,000
Maximum amount of sales attributable to a single customer | Rate										5.00%
Operating segment
Financial results of reportable segments
Sales										$ 317,920,000	292,013,000	315,249,000
Depreciation and amortization										7,515,000	7,819,000	8,782,000
Segment (loss) income										16,925,000	9,970,000	10,737,000
Capital expenditures										3,207,000	2,479,000	4,195,000
Segment assets	[1]	269,679,000				265,279,000				269,679,000	265,279,000	274,334,000
Reconciliation of segment income to consolidated income before income taxes
Unallocated corporate expense										(7,991,000)	(6,575,000)	(5,800,000)
Interest expense, net										(251,000)	(328,000)	(499,000)
Other unallocated income (expense)										0	0	0
Income from continuing operations before income taxes										8,683,000	3,067,000	4,438,000
Operating segment | MMS
Financial results of reportable segments
Sales										251,906,000	230,705,000	250,854,000
Depreciation and amortization										5,566,000	5,764,000	6,497,000
Segment (loss) income										5,803,000	3,060,000	7,365,000
Capital expenditures										2,745,000	1,943,000	3,186,000
Segment assets	[1]	224,717,000				219,503,000				224,717,000	219,503,000	226,265,000
Operating segment | ATA
Financial results of reportable segments
Sales										66,551,000	61,647,000	65,128,000
Depreciation and amortization										1,949,000	2,055,000	2,285,000
Segment (loss) income										11,122,000	6,910,000	3,372,000
Capital expenditures										462,000	536,000	1,009,000
Segment assets	[1]	44,962,000				45,776,000				44,962,000	45,776,000	48,069,000
Inter-Segment Eliminations
Financial results of reportable segments
Sales										(537,000)	(339,000)	(733,000)
Unallocated assets
Financial results of reportable segments
Segment assets		49,270,000				32,271,000				49,270,000	32,271,000	36,604,000
Reconciliation of segment income to consolidated income before income taxes
Cash		$ 45,000,000				$ 28,300,000				45,000,000	$ 28,300,000	$ 32,800,000
Minimum | MMS
Reconciliation of segment income to consolidated income before income taxes
Average selling price										30,000
Minimum | ATA
Reconciliation of segment income to consolidated income before income taxes
Average selling price										40
Maximum | MMS
Reconciliation of segment income to consolidated income before income taxes
Average selling price										2,000,000
Maximum | ATA
Reconciliation of segment income to consolidated income before income taxes
Average selling price										$ 200,000

[1] Segment assets primarily consist of restricted cash, accounts receivable, inventories, prepaid and other assets, property, plant and equipment, and intangible assets. Unallocated assets primarily include, cash and cash equivalents, corporate property, plant and equipment, deferred income taxes, and other non-current assets.