BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Lessor, Lease, Description [Line Items]
Operating Leases, Income Statement, Lease Revenue, Total		$ 41,436
Operating Leases, Lease Income [Abstract]
Rental revenue	$ 44,826
Lease income - operating leases		40,225
Non-lease components	0	$ 1,211
Total lease income - included in Revenue	44,826
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
2019 (remainder)	2,751
2020	3,349
2021	3,356
2022	3,344
2023	3,108
Thereafter	7,967
Total	$ 23,875
Minimum
Lessor, Lease, Description [Line Items]
Term of contract	3 years
Maximum
Lessor, Lease, Description [Line Items]
Term of contract	15 years