GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Summary of goodwill amount
Goodwill	$ 39,111	$ 39,111
Accumulated impairment losses	(32,434)	(32,434)
Balance at December 31, 2017	6,677
Accumulated impairment losses	(31)
Balance at March 31, 2018	6,646
MMS
Summary of goodwill amount
Goodwill	32,434	32,434
Accumulated impairment losses	(32,434)	(32,434)
Balance at December 31, 2017	0
Accumulated impairment losses	0
Balance at March 31, 2018	0
ATA
Summary of goodwill amount
Goodwill	6,677	6,677
Accumulated impairment losses	0	$ 0
Balance at December 31, 2017	6,677
Accumulated impairment losses	(31)
Balance at March 31, 2018	$ 6,646