UNAUDITED QUARTERLY INFORMATION (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
UNAUDITED QUARTERLY INFORMATION
Net Sales	$ 54,287	$ 51,929	$ 60,354	$ 49,929	$ 53,886	$ 51,404	$ 53,411	$ 50,539	$ 216,499	$ 209,240	$ 209,617
Gross Profit	20,361	20,970	24,248	18,561	22,274	21,311	20,853	20,101
Operating income (loss)	(8,557)	2,616	3,217	132	2,484	3,154	2,004	1,973	(2,592)	9,615	12,678
Other expense, net	(866)	(634)	(320)	(912)	(550)	(393)	(407)	(122)
(Loss) income from operations	(9,423)	1,982	2,897	(780)	1,934	2,761	1,597	1,851	(5,324)	8,143	10,468
Net (loss) income attributable to ISG	$ (8,150)	$ 732	$ 1,612	$ (699)	$ 1,276	$ 1,778	$ 934	$ 853	$ (6,505)	$ 4,841	$ 6,178
Basic (Loss) earnings per share attributable to ISG	$ (0.22)	$ 0.02	$ 0.05	$ (0.02)	$ 0.03	$ 0.05	$ 0.03	$ 0.02	$ (0.18)	$ 0.13	$ 0.17
Diluted (loss) earnings per share attributable to ISG	$ (0.22)	$ 0.02	$ 0.04	$ (0.02)	$ 0.03	$ 0.05	$ 0.02	$ 0.02	$ (0.18)	$ 0.13	$ 0.16
Basic Weighted Average Common shares	37,842	35,707	35,609	37,340	37,198	37,315	37,199	37,032	36,625	37,186	37,086
Diluted weighted average common shares	37,842	36,873	36,719	37,340	38,986	39,296	38,971	38,490	36,625	38,936	38,693