RECEIVABLES (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Receivables [Abstract]
Trade accounts receivable		$ 167,409	$ 192,743
Unbilled receivables		66,376	62,864
Allowance for doubtful accounts		(9,674)	(9,990)
Total	[1]	$ 224,111	$ 245,617

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