Segment Operating Results - Revenues Derived from Clients by Geographical Areas (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Net Revenues	$ 407,084	$ 463,383
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	274,122	386,517
Europe and Other [Member]
Segment Reporting Information [Line Items]
Net Revenues	129,284	65,230
Latin America [Member]
Segment Reporting Information [Line Items]
Net Revenues	$ 3,678	$ 11,636