REVENUES - Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable and Allowance for Doubtful Accounts
Allowance for doubtful accounts, returns and credits	$ 20.4	$ 15.3
Activity in the allowance for doubtful accounts
Beginning balance	84.3	55.5
Bad debt expense	12.4	54.6
Write-offs	(23.7)	(25.0)
Other	3.4	(1.2)
Ending balance (b)	$ 76.4	88.2
Accounting Standards Update 2016-13 | Adjustment.
Activity in the allowance for doubtful accounts
Beginning balance		$ 4.3