RECEIVABLES (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Receivables [Abstract]
Trade accounts receivable		$ 176,583	$ 192,743
Unbilled receivables		47,411	62,864
Allowance for credit losses		(9,633)	(9,990)
Total	[1]	$ 214,361	$ 245,617

[1] Includes billed and unbilled amounts, net of allowance for credit losses. See Note 3 for details.