REVENUE - Net Sales by Product Category (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Total Sales	$ 309.4	$ 356.5	$ 923.5	$ 1,056.6
Office Segment
Revenue from External Customer [Line Items]
Total Sales	193.2	219.1	589.9	644.5
Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	116.2	137.4	333.6	412.1
Office Systems | Office Segment
Revenue from External Customer [Line Items]
Total Sales	84.7	111.2	268.6	332.3
Seating | Office Segment
Revenue from External Customer [Line Items]
Total Sales	25.7	32.3	77.4	97.8
Files and Storage | Office Segment
Revenue from External Customer [Line Items]
Total Sales	18.4	26.0	64.3	78.9
Ancillary | Office Segment
Revenue from External Customer [Line Items]
Total Sales	52.2	36.6	147.1	92.5
Other | Office Segment
Revenue from External Customer [Line Items]
Total Sales	12.2	13.0	32.5	43.0
Studio | Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	96.4	108.7	267.4	323.5
Coverings | Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	$ 19.8	$ 28.7	$ 66.2	$ 88.6