ACCOUNTS RECEIVABLE, NET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, net
Accounts receivable, gross	$ 48,087	$ 47,349
Less: Allowance for doubtful accounts	(4,472)	(10,883)
Total	43,615	36,466
Bad debt expense	720	2,830	$ 5,116
Billed
Accounts receivable, net
Accounts receivable, gross	35,921	35,590
Unbilled
Accounts receivable, net
Accounts receivable, gross	$ 12,166	$ 11,759