Segment Operating Results - Revenues Derived from Clients by Geographical Areas (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Net Revenues	$ 521,569	$ 447,306	$ 928,653	$ 910,689
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	386,545	346,225	660,667	732,742
Europe and Other [Member]
Segment Reporting Information [Line Items]
Net Revenues	130,144	91,933	259,428	157,163
Latin America [Member]
Segment Reporting Information [Line Items]
Net Revenues	$ 4,880	$ 9,148	$ 8,558	$ 20,784