EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 358,729			$ 358,729
Net earnings		$ 13,123	$ 12,960	28,390	$ 28,352
Other comprehensive income		(2,194)	$ 2,182	(2,959)	$ 2,525
Shares issued under stock incentive plan				2
Shares issued to Board of Directors in lieu of cash				37
Stock-based compensation, net of forfeitures				4,496
Cash dividend ($0.30 per share)				(15,238)
Purchase of common stock (in shares)				(4,395)
Ending Balance		369,062		$ 369,062
Cash dividend (in dollars per share)				$ 0.30
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	493			$ 493
Shares issued under stock incentive plan				4
Stock-based compensation, net of forfeitures				0
Purchase of common stock (in shares)				(2)
Ending Balance		495		495
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	54,455			54,455
Shares issued under stock incentive plan				(2)
Shares issued to Board of Directors in lieu of cash				37
Stock-based compensation, net of forfeitures				4,496
Purchase of common stock (in shares)				(4,393)
Ending Balance		54,593		54,593
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	347,304			347,304
Net earnings				28,383
Other comprehensive income				0
Cash dividend ($0.30 per share)				(15,238)
Ending Balance		366,699		366,699
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(43,774)			(43,774)
Other comprehensive income				(2,959)
Ending Balance		(52,983)		(52,983)
Total Knoll, Inc. Stockholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	358,478			358,478
Net earnings				28,383
Other comprehensive income				(2,959)
Shares issued under stock incentive plan				2
Shares issued to Board of Directors in lieu of cash				37
Stock-based compensation, net of forfeitures				4,496
Cash dividend ($0.30 per share)				(15,238)
Purchase of common stock (in shares)				(4,395)
Ending Balance		368,804		368,804
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	251			251
Net earnings				7
Ending Balance		$ 258		$ 258
ASU 2018-02
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2018-02	(6,250)
ASU 2018-02 | Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2018-02	$ 6,250