EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 358,729	$ 358,729
Net earnings		15,267	$ 15,396
Other comprehensive income		(765)	$ 343
Shares issued under stock incentive plan (261,167 shares)		2
Shares issued to Board of Directors in lieu of cash (1,238 shares)		25
Stock-based compensation, net of forfeitures		2,426
Cash dividend ($0.15 per share)		(7,338)
Purchase of common stock (95,412 shares)		(1,952)
Ending Balance		$ 366,394
Shares issued under stock incentive plan (in shares)		261,167
Shares issued to Board of Directors in lieu of cash (in shares)		1,238
Cash dividend (in dollars per share)		$ 0.15
Purchase of common stock (in shares)		95,412
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	493	$ 493
Shares issued under stock incentive plan (261,167 shares)		3
Stock-based compensation, net of forfeitures		0
Purchase of common stock (95,412 shares)		(1)
Ending Balance		495
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	54,455	54,455
Shares issued under stock incentive plan (261,167 shares)		(1)
Shares issued to Board of Directors in lieu of cash (1,238 shares)		25
Stock-based compensation, net of forfeitures		2,426
Purchase of common stock (95,412 shares)		(1,951)
Ending Balance		54,954
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	347,304	347,304
Net earnings		15,259
Other comprehensive income		0
Cash dividend ($0.15 per share)		(7,338)
Ending Balance		361,475
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(43,774)	(43,774)
Other comprehensive income		(765)
Ending Balance		(50,789)
Total Knoll, Inc. Stockholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	358,478	358,478
Net earnings		15,259
Other comprehensive income		(765)
Shares issued under stock incentive plan (261,167 shares)		2
Shares issued to Board of Directors in lieu of cash (1,238 shares)		25
Stock-based compensation, net of forfeitures		2,426
Cash dividend ($0.15 per share)		(7,338)
Purchase of common stock (95,412 shares)		(1,952)
Ending Balance		366,135
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	251	251
Net earnings		8
Ending Balance		$ 259
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
ASU 2018-02 | Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2018-02	$ (6,250)