REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 1,917,815	$ 1,105,941	$ 5,493,365	$ 2,924,131
Americas
Disaggregation of Revenue [Line Items]
Revenues	1,598,986	867,336	4,631,520	2,261,677
Europe
Disaggregation of Revenue [Line Items]
Revenues	268,169	179,913	720,253	483,131
Asia Pacific
Disaggregation of Revenue [Line Items]
Revenues	50,660	58,692	141,592	179,323
Operating Segments | Merchant Solutions
Disaggregation of Revenue [Line Items]
Revenues	1,243,961	1,004,943	3,460,785	2,812,640
Operating Segments | Merchant Solutions | Relationship-led
Disaggregation of Revenue [Line Items]
Revenues	709,749	538,112	1,934,265	1,499,393
Operating Segments | Merchant Solutions | Technology-enabled
Disaggregation of Revenue [Line Items]
Revenues	534,212	466,831	1,526,520	1,313,247
Operating Segments | Merchant Solutions | Americas
Disaggregation of Revenue [Line Items]
Revenues	1,039,039	786,659	2,926,472	2,181,000
Operating Segments | Merchant Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenues	154,262	159,592	392,721	452,317
Operating Segments | Merchant Solutions | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenues	50,660	58,692	141,592	179,323
Operating Segments | Issuer Solutions
Disaggregation of Revenue [Line Items]
Revenues	487,409	75,628	1,461,196	86,122
Operating Segments | Issuer Solutions | Americas
Disaggregation of Revenue [Line Items]
Revenues	370,938	55,091	1,127,832	55,092
Operating Segments | Issuer Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenues	113,907	20,321	327,532	30,814
Operating Segments | Issuer Solutions | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenues	2,564	216	5,832	216
Operating Segments | Business and Consumer Solutions
Disaggregation of Revenue [Line Items]
Revenues	204,106	27,896	624,774	27,896
Operating Segments | Business and Consumer Solutions | Americas
Disaggregation of Revenue [Line Items]
Revenues	204,106	27,896	624,774	27,896
Operating Segments | Business and Consumer Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | Business and Consumer Solutions | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(17,661)	(2,526)	(53,390)	(2,527)
Intersegment Eliminations | Americas
Disaggregation of Revenue [Line Items]
Revenues	(15,097)	(2,310)	(47,558)	(2,311)
Intersegment Eliminations | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenues	$ (2,564)	$ (216)	$ (5,832)	$ (216)