ACQUISITIONS AND DROP DOWN TRANSACTIONS - 2016 Drop Down (Details) - USD ($) $ in Thousands		1 Months Ended
	Mar. 03, 2016	Jun. 30, 2016	Sep. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Deferred purchase price obligation			$ 416,718	$ 362,959
Drop Down Assets 2016 Acquisition
Business Acquisition [Line Items]
Initial payment	$ 360,000
Working capital adjustment		$ 600
Estimated future payment obligation			470,900
Deferred purchase price obligation			$ 416,700
Discount rate			8.50%