SEGMENT INFORMATION - Schedule of Segment Revenues from Major Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	$ 371,182	$ 404,800	$ 728,165	$ 788,917
PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	354,474	388,141	693,639	757,037
Revenue | Customer Concentration Risk | Customer A | PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	68,370	76,415	130,241	163,241
Revenue | Customer Concentration Risk | Customer B | PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	139,811	66,422	262,930	97,126
Revenue | Customer Concentration Risk | Customer C | PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	$ 53,511	$ 57,474	$ 95,377	$ 109,687