NET INCOME PER COMMON SHARE - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic:
Net income attributable to ISG	$ 1,428	$ 732	$ 520	$ 1,645
Weighted average common shares	43,305	35,707	42,893	36,219
Earnings per share attributable to ISG	$ 0.03	$ 0.02	$ 0.01	$ 0.05
Diluted:
Net income attributable to ISG	$ 1,428	$ 732	$ 520	$ 1,645
Interest expense of convertible debt, net of tax	2	1	6	21
Net income attributable to ISG, as adjusted	$ 1,430	$ 733	$ 526	$ 1,666
Basic weighted average common shares	43,305	35,707	42,893	36,219
Potential common shares	1,353	1,166	451	758
Diluted weighted average common shares	44,658	36,873	43,344	36,977
Diluted earnings per share attributable to ISG	$ 0.03	$ 0.02	$ 0.01	$ 0.05