CONTRACT BALANCES (Schedule of Changes in Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 7,686	$ 8,685
Add: provision for doubtful accounts	26,802	15,259
Less: write-offs, net of recoveries	(23,172)	(16,165)
Balance, end of period	$ 11,316	$ 7,779