CONTRACT BALANCES (Schedule of Changes in Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	[2]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	[1]	$ 8,602
Add: bad debt expense		19,285	$ 15,239
Less: write-offs, net of recoveries		(19,002)
Balance, end of period		$ 8,885

[1] As of January 1, 2018, the Company adopted Accounting Standards Update 2014-09, "Revenue from Contracts with Customers (Topic 606)" ("ASC 606"), using the full retrospective method. Accordingly, the Company has recast certain amounts in the prior period presented. See Note 1 below for additional discussion.

[2] As of January 1, 2018, the Company adopted ASC 606 using the full retrospective method. Accordingly, the Company has recast certain amounts in the prior period presented. Also as of January 1, 2018, the Company adopted Accounting Standards Update No. 2016-18, "Statement of Cash Flows (Subtopic 230): Restricted Cash," and recast the prior period presented. See Note 1 below for additional discussion.