REVENUE - Net Sales by Product Category (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue from External Customer [Line Items]
Total Sales	$ 340.0	$ 332.8
Office Segment
Revenue from External Customer [Line Items]
Total Sales	216.4	202.2
Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	123.6	130.6
Office Systems | Office Segment
Revenue from External Customer [Line Items]
Total Sales	100.9	106.3
Seating | Office Segment
Revenue from External Customer [Line Items]
Total Sales	30.4	30.9
Files and Storage | Office Segment
Revenue from External Customer [Line Items]
Total Sales	25.2	25.6
Ancillary | Office Segment
Revenue from External Customer [Line Items]
Total Sales	49.3	25.5
Other | Office Segment
Revenue from External Customer [Line Items]
Total Sales	10.6	13.9
Studio | Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	96.3	101.6
Coverings | Lifestyle Segment
Revenue from External Customer [Line Items]
Total Sales	$ 27.3	$ 29.0