SEGMENTS INFORMATION - Major Customers (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017
Revenue, Major Customer [Line Items]
Revenues	$ 445,647	$ 348,977	$ 869,795	$ 673,628
Operating Segments
Revenue, Major Customer [Line Items]
Revenues	$ 445,978	$ 349,021	$ 870,303	$ 673,724
Sales Revenue, Net | Customer Concentration Risk | Operating Segments
Revenue, Major Customer [Line Items]
Number of customers	0	0	0	0
Accounts Receivable | Customer Concentration Risk | Billed Revenues
Revenue, Major Customer [Line Items]
Number of customers			0		0
Accounts Receivable | Customer Concentration Risk | Unbilled Revenues
Revenue, Major Customer [Line Items]
Number of customers			1		1
Concentration percentage			10.20%		13.00%