NET (LOSS) INCOME PER COMMON SHARE - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Basic:
Net (loss) income attributable to ISG	$ (699)	$ 853
Weighted average common shares	37,340	37,032
(Loss) earnings per share attributable to ISG	$ (0.02)	$ 0.02
Diluted:
Net (loss) income attributable to ISG	$ (699)	$ 853
Interest expense of convertible debt, net of tax		16
Net (loss) income, attributable to ISG, as adjusted	$ (699)	$ 869
Basic Weighted Average Common shares	37,340	37,032
Potential common shares		1,458
Diluted weighted average common shares	37,340	38,490
Diluted (loss) earnings per share attributable to ISG	$ (0.02)	$ 0.02