SEGMENTS INFORMATION - Major Customers (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Revenue, Major Customer [Line Items]
Revenues	$ 377,523	$ 298,293	$ 1,051,151	$ 846,607
Operating Segments
Revenue, Major Customer [Line Items]
Revenues	378,290	298,354	1,052,014	847,145
Operating Segments | Europe
Revenue, Major Customer [Line Items]
Revenues	$ 157,446	$ 126,265	$ 431,472	$ 349,834
Sales Revenue, Net | Customer Concentration Risk | Operating Segments
Revenue, Major Customer [Line Items]
Number of customers	0		0
Sales Revenue, Net | Customer Concentration Risk | Operating Segments | Europe | UBS AG
Revenue, Major Customer [Line Items]
Number of customers		1		1
Revenues		$ 35,142		$ 107,381
Accounts Receivable | Customer Concentration Risk | UBS AG | Billed Revenues
Revenue, Major Customer [Line Items]
Number of customers			1
Concentration percentage			10.50%
Accounts Receivable | Customer Concentration Risk | Expedia | Unbilled Revenues
Revenue, Major Customer [Line Items]
Number of customers			1
Concentration percentage			10.90%