RECEIVABLES - Summary of Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Trade accounts receivable	$ 157,513	$ 192,743
Unbilled revenues	46,471	62,864
Allowance for credit losses	(9,918)	(9,990)		$ (15,182)	$ (11,308)
Total	$ 194,066	$ 245,617	[1]

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