OTHER CURRENT ASSETS AND OTHER ASSETS - Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
OTHER CURRENT ASSETS AND OTHER ASSETS
Income tax receivable	$ 13,200	$ 10,999	$ 41,736	$ 41,066	$ 34,735	$ 15,899	$ 16,750	$ 9,696
Non-trade receivables	6,223				9,961
Prepaid rent	4,070				73
Prepaid maintenance	3,914				3,567
Restricted cash	2,255				3,870
Prepaid other	1,542				1,247
Prepaid education and training	398				1,186
Prepaid insurance	447				344
Other	288				822
Total other current assets	$ 19,137	$ 18,102	$ 19,199	$ 24,014	$ 21,070	$ 22,603	$ 20,907	$ 23,242