REVENUE - Net Sales by Product Category (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue from External Customer [Line Items]
Total Sales	$ 274.1	$ 367.3	$ 614.1	$ 700.1
Office Segment
Revenue from External Customer [Line Items]
Total Sales	180.3	223.2	396.7	425.4
Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	93.8	144.1	217.4	274.7
Office Systems | Office Segment
Revenue from External Customer [Line Items]
Total Sales	83.0	114.8	183.9	221.1
Seating | Office Segment
Revenue from External Customer [Line Items]
Total Sales	21.3	34.6	51.7	65.5
Files and Storage | Office Segment
Revenue from External Customer [Line Items]
Total Sales	20.7	27.4	45.9	52.9
Ancillary | Office Segment
Revenue from External Customer [Line Items]
Total Sales	45.6	30.3	94.9	55.9
Other | Office Segment
Revenue from External Customer [Line Items]
Total Sales	9.7	16.1	20.3	30.0
Studio | Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	74.7	113.3	171.0	214.8
Coverings | Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	$ 19.1	$ 30.8	$ 46.4	$ 59.9