SEGMENT AND GEOGRAPHIC REGION INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting [Abstract]
Number of reportable segments									3
Net sales by product category
Net sales	$ 286,453	$ 268,297	$ 265,943	$ 229,601	$ 230,456	$ 216,898	$ 214,312	$ 200,586	$ 1,050,294	$ 862,252	$ 898,496
Office Systems
Net sales by product category
Net sales									429,503	392,700	432,124
Seating
Net sales by product category
Net sales									108,635	109,650	104,388
Files and Storage
Net sales by product category
Net sales									84,297	68,185	79,108
Studio
Net sales by product category
Net sales									279,167	154,083	147,550
Coverings
Net sales by product category
Net sales									114,899	109,038	106,628
Other
Net sales by product category
Net sales									$ 33,793	$ 28,596	$ 28,698