COMMON STOCK AND EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net earnings attributable to Knoll, Inc. stockholders	$ 21,607	$ 17,833	$ 60,642	$ 52,515
Denominator for basic earnings per share - weighted-average shares	48,053,836	47,764,462	48,000,386	47,725,186
Potentially dilutive shares resulting from stock plans (in shares)	792,000	724,000	766,000	716,000
Denominator for diluted earnings per share - weighted-average shares (in shares)	48,845,553	48,487,623	48,765,607	48,441,129
Antidilutive equity awards not included in weighted-average common shares—diluted (in shares)	(8,000)	0	(43,000)	0
Basic (in dollars per share)	$ 0.45	$ 0.37	$ 1.26	$ 1.10
Diluted (in dollars per share)	$ 0.44	$ 0.37	$ 1.24	$ 1.08