BUSINESS DESCRIPTION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounts Receivable and Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Activity in the entity's accounts receivable allowance
Balance at beginning of year	$ 4,421	$ 6,667	$ 2,813
Provision charged to expense	9,347	8,793	7,072
Write-offs, less recoveries	(9,219)	(11,039)	(6,516)
Acquired allowance for doubtful accounts			3,298
Balance at end of year	$ 4,549	$ 4,421	$ 6,667