EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net earnings attributable to Knoll, Inc. stockholders	$ 32,693	$ 19,132	$ 12,934	$ 15,404	$ 21,442	$ 21,607	$ 21,635	$ 17,400	$ 80,163	$ 82,084	$ 65,963
Denominator for basic earnings per share - weighted-average shares (in shares)									48,422,558	48,093,294	47,746,707
Potentially dilutive shares resulting from stock plans (in shares)									737,000	826,000	691,000
Denominator for diluted earnings per share - weighted-average shares (in shares)									49,160,492	48,919,108	48,438,231
Antidilutive equity awards not included in weighted-average common shares—diluted (in shares)									0	0	4,000
Basic (in dollars per share)	$ 0.67	$ 0.39	$ 0.27	$ 0.32	$ 0.45	$ 0.45	$ 0.45	$ 0.36	$ 1.66	$ 1.71	$ 1.38
Diluted (in dollars per share)	$ 0.67	$ 0.39	$ 0.26	$ 0.31	$ 0.44	$ 0.44	$ 0.44	$ 0.36	$ 1.63	$ 1.68	$ 1.36