Segment Operating Results - Revenues Derived from Clients by Geographical Areas (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Net Revenues	$ 447,306	$ 373,255	$ 910,689	$ 760,485
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	346,225	274,652	732,742	537,752
Europe and Other [Member]
Segment Reporting Information [Line Items]
Net Revenues	91,933	96,589	157,163	219,500
Latin America [Member]
Segment Reporting Information [Line Items]
Net Revenues	$ 9,148	$ 2,014	$ 20,784	$ 3,233