REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2,280,906	$ 2,137,437	$ 4,437,160	$ 4,127,444
Americas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,915,182	1,789,852	3,719,026	3,472,094
Europe
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	305,689	290,444	601,755	543,742
Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	60,035	57,141	116,379	111,608
Operating Segments | Merchant Solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,581,716	1,426,755	3,054,735	2,694,627
Operating Segments | Merchant Solutions | Relationship-led
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	827,577	778,978	1,564,982	1,445,890
Operating Segments | Merchant Solutions | Technology-enabled
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	754,139	647,777	1,489,753	1,248,737
Operating Segments | Merchant Solutions | Americas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,334,231	1,202,970	2,576,851	2,283,440
Operating Segments | Merchant Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	187,450	166,644	361,505	299,578
Operating Segments | Merchant Solutions | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	60,035	57,141	116,379	111,609
Operating Segments | Issuer Solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	534,471	505,932	1,045,972	1,006,183
Operating Segments | Issuer Solutions | Americas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	412,023	379,121	797,266	757,164
Operating Segments | Issuer Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	114,011	120,974	231,682	238,386
Operating Segments | Issuer Solutions | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8,437	5,837	17,024	10,633
Operating Segments | Business and Consumer Solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	187,632	227,355	383,404	470,941
Operating Segments | Business and Consumer Solutions | Americas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	183,404	224,529	374,836	465,163
Operating Segments | Business and Consumer Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4,228	2,826	8,568	5,778
Operating Segments | Business and Consumer Solutions | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(22,913)	(22,605)	(46,951)	(44,307)
Intersegment Eliminations | Americas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(14,476)	(16,768)	(29,927)	(33,673)
Intersegment Eliminations | Europe
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Intersegment Eliminations | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ (8,437)	$ (5,837)	$ (17,024)	$ (10,634)