ACQUISITIONS - Narrative (Details) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)
Business Acquisition [Line Items]
Goodwill acquired		$ 23,000
TSYS
Business Acquisition [Line Items]
Adjustment to goodwill		(65,559)
Goodwill acquired		17,300,000
Revenue of acquiree	$ 997,000	2,052,000
Operating income (loss) of acquiree	103,800	219,300
Employee termination benefits obligation	37,700	37,700	$ 37,700
Employee termination benefits charges	24,100	41,700	98,800
Employee termination benefits charges related to stock-based compensation	$ 1,700	4,200	$ 21,600
Merchant Solutions
Business Acquisition [Line Items]
Goodwill acquired		23,000
Merchant Solutions | TSYS
Business Acquisition [Line Items]
Goodwill acquired		7,100,000
Issuer Solutions
Business Acquisition [Line Items]
Goodwill acquired		0
Issuer Solutions | TSYS
Business Acquisition [Line Items]
Goodwill acquired		7,900,000
Business and Consumer Solutions
Business Acquisition [Line Items]
Goodwill acquired		0
Business and Consumer Solutions | TSYS
Business Acquisition [Line Items]
Goodwill acquired		$ 2,300,000