Segment Operating Results - Revenues Derived from Clients by Geographical Areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net Revenues	$ 1,983,383	$ 2,063,425	$ 1,635,517
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,464,551	1,591,883	1,199,231
Europe And Other [Member]
Segment Reporting Information [Line Items]
Net Revenues	501,425	438,602	422,271
Latin America [Member]
Segment Reporting Information [Line Items]
Net Revenues	$ 17,407	$ 32,940	$ 14,015