PENSION AND POST-RETIREMENT BENEFITS - Classification of Net Periodic Pension (Income) Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total net periodic benefit costs	$ 1.3	$ 1.5	$ 3.6	$ 4.2	$ 4.0
Selling, general and administrative expense
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total net periodic benefit costs	0.4	0.5	1.1	1.3
Miscellaneous, net
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total net periodic benefit costs	$ 0.9	$ 1.0	$ 2.5	$ 2.9