UNAUDITED QUARTERLY INFORMATION (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
UNAUDITED QUARTERLY INFORMATION                      
Net Sales $ 53,886 $ 51,404 $ 53,411 $ 50,539 $ 53,230 $ 53,258 $ 54,888 $ 48,241 $ 209,240 $ 209,617 $ 210,982
Gross Profit 22,274 21,311 20,853 20,101 21,894 21,771 23,391 18,429      
Operating income 2,484 3,154 2,004 1,973 3,346 3,772 4,524 1,036 9,615 12,678 11,701
Other expense, net (550) (393) (407) (122) (732) (574) (374) (530)      
Income from operations 1,934 2,761 1,597 1,851 2,614 3,198 4,150 506 8,143 10,468 9,043
Net income attributable to ISG $ 1,276 $ 1,778 $ 934 $ 853 $ 657 $ 2,353 $ 3,105 $ 63 $ 4,841 $ 6,178 $ 4,776
Earnings per share attributable to ISG $ 0.03 $ 0.05 $ 0.03 $ 0.02 $ 0.02 $ 0.06 $ 0.08 $ 0.00 $ 0.13 $ 0.17 $ 0.13
Diluted earnings per share attributable to ISG $ 0.03 $ 0.05 $ 0.02 $ 0.02 $ 0.02 $ 0.06 $ 0.08 $ 0.00 $ 0.13 $ 0.16 $ 0.13
Basic Weighted Average Common shares 37,198 37,315 37,199 37,032 36,702 37,039 37,220 37,383 37,186 37,086 36,810
Diluted weighted average common shares 38,986 39,296 38,971 38,490 38,333 38,740 38,837 38,861 38,936 38,693 38,687