SEGMENT AND GEOGRAPHIC REGION INFORMATION (Details 2) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment									3
Net sales by product category
Net sales	$ 305,734	$ 263,588	$ 268,622	$ 266,498	$ 286,453	$ 268,297	$ 265,943	$ 229,601	$ 1,104,442	$ 1,050,294	$ 862,252
Office Systems
Net sales by product category
Net sales									432,655	429,503	392,700
Seating
Net sales by product category
Net sales									117,799	108,635	109,650
Files and Storage
Net sales by product category
Net sales									86,099	84,297	68,185
Studio
Net sales by product category
Net sales									303,838	279,167	154,083
Coverings
Net sales by product category
Net sales									113,661	114,899	109,038
Other
Net sales by product category
Net sales									$ 50,390	$ 33,793	$ 28,596