| SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Rollforward of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions | 12 Months Ended | |
|---|---|---|
| Dec. 31, 2020 | Dec. 31, 2019 | |
| Accounts Receivable, Allowance for Credit Loss [Roll Forward] | ||
| Allowance for doubtful accounts, beginning of period | $ 11.2 | $ 10.9 | 
| Current period bad debt expense | 6.3 | 5.4 | 
| Write-offs, net of recoveries | (4.6) | (5.1) | 
| Allowance for doubtful accounts, end of period | $ 12.9 | $ 11.2 | 
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- Definition Amount of allowance for credit loss on accounts receivable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available. 
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- Definition Amount of direct write-downs of accounts receivable charged against the allowance. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of expense (reversal of expense) for expected credit loss on accounts receivable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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