Segment Operating Results - Revenues Derived from Clients by Geographical Areas (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net Revenues	$ 463,383	$ 387,230
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	386,517	263,100
Europe and Other [Member]
Segment Reporting Information [Line Items]
Net Revenues	65,230	122,911
Latin America [Member]
Segment Reporting Information [Line Items]
Net Revenues	$ 11,636	$ 1,219