COMMON STOCK AND EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net earnings attributable to Knoll, Inc. stockholders	$ 19,132	$ 21,607	$ 47,470	$ 60,642
Weighted-average shares of common stock outstanding—basic (in shares)	48,468,480	48,053,836	48,406,659	48,000,386
Potentially dilutive shares resulting from stock plans (in shares)	511,000	792,000	761,000	766,000
Denominator for diluted earnings per share - weighted-average shares (in shares)	48,979,182	48,845,553	49,167,856	48,765,607
Antidilutive equity awards not included in weighted-average common shares—diluted (in shares)	34,000	8,000	15,000	43,000
Basic (in dollars per share)	$ 0.39	$ 0.45	$ 0.98	$ 1.26
Diluted (in dollars per share)	$ 0.39	$ 0.44	$ 0.96	$ 1.24