INCOME TAXES - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Long-term deferred income tax (liabilities) assets:
Property and equipment	$ 50,405	$ 43,554
Goodwill	1,071	1,392
Intangible assets	(26,534)	(22,021)
Deferred revenue, less current portion	1,358	1,834
Restructuring liability, less current portion	696	1,282
Refinance	(4,130)	(374)
Deferred rent	285	639
Stock-based compensation	1,450	911
Provision for doubtful accounts	1,360	1,772
U.S. net operating loss carryforwards	99,026	89,117
Foreign net operating loss carryforwards, less current portion	7,631	8,053
Tax credit carryforwards	2,775	2,812
Interest limitation	9,403	0
Impact of adoption of ASC 606	(6,666)	0
Other	2,408	2,090
Long-term deferred income tax assets	140,538	131,061
Less: valuation allowance	(142,749)	(132,712)	$ (164,865)	$ (148,310)
Net deferred tax liabilities	$ (2,211)	$ (1,651)