EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net earnings attributable to Knoll, Inc. stockholders	$ 15,259	$ 15,404
Weighted-average shares of common stock outstanding—basic (in shares)	48,556,686	48,456,225
Potentially dilutive shares resulting from stock plans (in shares)	648,000	927,000
Denominator for diluted earnings per share - weighted-average shares (in shares)	49,204,776	49,382,892
Antidilutive equity awards not included in weighted-average common shares—diluted (in shares)	1,000	12,000
Basic (in dollars per share)	$ 0.31	$ 0.32
Diluted (in dollars per share)	$ 0.31	$ 0.31