VALUATION AND QUALIFYING ACCOUNTS (Tables)

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts [Abstract]

Schedule of Valuation and Qualifying Accounts

The following table summarizes the activity and ending balances in our allowance for doubtful accounts and estimated revenue adjustments (amounts in millions):

Allowance for Doubtful Accounts

Year End	Balance at Beginning of Year		Provision for Doubtful Accounts		Write-Offs			Balance at End of Year
2017	$	17.7	$	25.1	$	(21.9	)	$	20.9
2016	16.5		19.5		(18.3		)	17.7
2015	14.3		14.1		(11.9		)	16.5

Estimated Revenue Adjustments

Year End	Balance at Beginning of Year		Provision for Estimated Revenue Adjustments		Write-Offs			Balance at End of Year
2017	$	4.1	$	14.4	$	(12.3	)	$	6.2
2016	4.0		7.9		(7.8		)	4.1
2015	3.1		6.1		(5.2		)	4.0