Segment Information - Selected Financial Data, Revenues and Long lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 315,883	$ 354,901	$ 907,278	$ 858,374
Long-lived assets
Long-lived assets	2,201,706		2,201,706		$ 2,285,547
Bill Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	149,385	154,285	440,193	348,592
Digital Channels
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	14,473	15,271	45,528	61,240
Merchant Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	28,921	23,273	79,050	73,213
Payments Intelligence
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	17,886	22,382	46,806	53,778
Real-Time Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	13,163	20,223	57,415	58,271
Retail Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	92,055	119,467	238,286	263,280
Americas - United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	199,209	230,158	611,383	541,137
Long-lived assets
Long-lived assets	1,469,111		1,469,111		1,526,046
Americas - Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	15,014	25,147	39,857	53,355
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	79,312	84,853	190,135	204,019
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	22,348	14,743	65,903	59,863
Other
Long-lived assets
Long-lived assets	732,595		732,595		$ 759,501
Operating Segments | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	190,369	192,952	563,892	475,299
Operating Segments | ACI On Demand | Bill Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	149,385	154,285	440,193	348,592
Operating Segments | ACI On Demand | Digital Channels
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	8,583	8,480	24,304	36,280
Operating Segments | ACI On Demand | Merchant Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	20,720	18,534	61,147	55,815
Operating Segments | ACI On Demand | Payments Intelligence
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	9,037	8,759	29,902	26,614
Operating Segments | ACI On Demand | Real-Time Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	806	1,032	2,807	2,557
Operating Segments | ACI On Demand | Retail Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,838	1,862	5,539	5,441
Operating Segments | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	125,514	161,949	343,386	383,075
Operating Segments | ACI On Premise | Bill Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	0	0	0	0
Operating Segments | ACI On Premise | Digital Channels
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	5,890	6,791	21,224	24,960
Operating Segments | ACI On Premise | Merchant Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	8,201	4,739	17,903	17,398
Operating Segments | ACI On Premise | Payments Intelligence
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	8,849	13,623	16,904	27,164
Operating Segments | ACI On Premise | Real-Time Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	12,357	19,191	54,608	55,714
Operating Segments | ACI On Premise | Retail Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	90,217	117,605	232,747	257,839
Operating Segments | Americas - United States | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	170,817	176,172	505,191	425,033
Operating Segments | Americas - United States | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	28,392	53,986	106,192	116,104
Operating Segments | Americas - Other | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	2,750	2,268	8,402	7,118
Operating Segments | Americas - Other | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	12,264	22,879	31,455	46,237
Operating Segments | EMEA | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	14,564	12,191	42,006	36,751
Operating Segments | EMEA | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	64,748	72,662	148,129	167,268
Operating Segments | Asia Pacific | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	2,238	2,321	8,293	6,397
Operating Segments | Asia Pacific | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 20,110	$ 12,422	$ 57,610	$ 53,466