SEGMENT INFORMATION - Schedule of Segment Revenues from Major Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	$ 321,444	$ 313,355	$ 1,049,609	$ 1,102,272
PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	305,141	297,240	998,780	1,054,277
Revenue | Customer Concentration Risk | Customer A | PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	49,772	46,727	180,014	209,968
Revenue | Customer Concentration Risk | Customer B | PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	95,953	84,110	358,882	181,236
Revenue | Customer Concentration Risk | Customer C | PAMC
Revenue, Major Customer [Line Items]
Revenue from contracts with customers	$ 63,526	$ 59,364	$ 158,903	$ 169,052