COMMON STOCK AND EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net earnings attributable to Knoll, Inc. stockholders	$ 12,938	$ 21,635		$ 28,338	$ 39,035
Weighted-average shares of common stock outstanding—basic (in shares)	48,464,605	48,018,733		48,375,241	47,961,661
Potentially dilutive shares resulting from stock plans (in shares)	912,000	814,000		920,000	752,000
Denominator for diluted earnings per share - weighted-average shares (in shares)	49,376,506	48,832,874	48,833,000	49,294,525	48,713,633
Antidilutive equity awards not included in weighted-average common shares—diluted (in shares)	0	0		12,000	0
Basic (in dollars per share)	$ 0.27	$ 0.45		$ 0.59	$ 0.81
Diluted (in dollars per share)	$ 0.26	$ 0.44		$ 0.57	$ 0.80