EQUITY - Schedule of Change in Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 392.8	$ 386.5		$ 386.5
Net earnings (loss)	$ (9.6)		21.7	18.0	$ 1.3	39.6
Other comprehensive (loss) income	$ 8.7		0.0	(3.6)	(15.2)	(3.6)
Stock-based compensation, net			2.4	2.2
Dividends declared			(8.6)	(7.5)
Purchase of common stock				(3.0)
Other			0.1	0.2
Ending balance			$ 408.4	$ 392.8		408.4
Dividends declared (in dollars per share)	$ 0.04	$ 0.17	$ 0.17	$ 0.15
Purchase of common stock, shares (in shares)	3,130	154,012		141,738
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 0.5	$ 0.5	$ 0.5	$ 0.5	0.5	0.5
Ending balance	0.5	0.5	0.5	0.5	0.5	0.5
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	64.4	66.8	58.4	58.8	66.8	58.8
Stock-based compensation, net	3.3	1.6	2.4	2.2
Purchase of common stock		(4.0)		(3.0)
Other			0.1	0.4
Ending balance	67.7	64.4	60.9	58.4	67.7	60.9
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	432.1	429.7	405.9	395.4	429.7	395.4
Net earnings (loss)	(9.6)	10.9	21.7	18.0
Dividends declared	(1.4)	(8.5)	(8.6)	(7.5)
Ending balance	421.1	432.1	419.0	405.9	421.1	419.0
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(93.3)	(69.4)	(72.0)	(68.4)	(69.4)	(68.4)
Other comprehensive (loss) income	8.7	(23.9)		(3.6)
Ending balance	(84.6)	(93.3)	(72.0)	(72.0)	(84.6)	(72.0)
Total Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	403.7	427.6	392.8	386.3	427.6	386.3
Net earnings (loss)	(9.6)	10.9	21.7	18.0
Other comprehensive (loss) income	8.7	(23.9)		(3.6)
Stock-based compensation, net	3.3	1.6	2.4	2.2
Dividends declared	(1.4)	(8.5)	(8.6)	(7.5)
Purchase of common stock		(4.0)		(3.0)
Other			0.1	0.4
Ending balance	$ 404.7	$ 403.7	408.4	392.8	$ 404.7	408.4
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			0.0	0.2		0.2
Other				(0.2)
Ending balance			$ 0.0	$ 0.0		$ 0.0

KNOLL INC 10-Q