Segment Information - Selected Financial Data, Revenues and Long lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 297,618	$ 234,995	$ 503,473	$ 444,305
Long-lived assets
Long-lived assets	2,264,768		2,264,768		$ 1,528,930
Bill Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	125,339	74,371	194,306	140,539
Digital Channels
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	27,455	19,227	45,968	41,234
Merchant Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	25,579	20,719	49,940	39,340
Payments Intelligence
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	15,378	18,221	31,396	39,199
Real-Time Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	22,716	16,225	38,049	30,316
Retail Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	81,151	86,232	143,814	153,677
Americas - United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	191,521	123,219	310,979	243,028
Long-lived assets
Long-lived assets	1,538,730		1,538,730		811,435
Americas - Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	14,520	14,124	28,208	33,228
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	64,647	74,914	119,166	125,609
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	26,930	22,738	45,120	42,440
Other [Member]
Long-lived assets
Long-lived assets	726,038		726,038		$ 717,495
Operating Segments | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	125,119	121,395	221,126	226,425
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	9,444	8,917	18,169	20,280
Operating Segments | ACI On Premise | Merchant Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	7,637	5,308	12,659	10,383
Operating Segments | ACI On Premise | Payments Intelligence
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	6,504	7,974	13,541	18,329
Operating Segments | ACI On Premise | Real-Time Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	21,809	15,741	36,524	29,382
Operating Segments | ACI On Premise | Retail Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	79,725	83,455	140,233	148,051
Operating Segments | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	172,499	113,600	282,347	217,880
Operating Segments | ACI On Demand | Bill Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	125,339	74,371	194,306	140,539
Operating Segments | ACI On Demand | Digital Channels
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	18,011	10,310	27,799	20,954
Operating Segments | ACI On Demand | Merchant Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	17,942	15,411	37,281	28,957
Operating Segments | ACI On Demand | Payments Intelligence
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	8,874	10,247	17,855	20,870
Operating Segments | ACI On Demand | Real-Time Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	907	484	1,525	934
Operating Segments | ACI On Demand | Retail Payments
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,426	2,777	3,581	5,626
Operating Segments | Americas - United States | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	35,696	25,394	62,118	56,258
Operating Segments | Americas - United States | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	155,825	97,825	248,861	186,770
Operating Segments | Americas - Other | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	12,413	11,776	23,358	28,560
Operating Segments | Americas - Other | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	2,107	2,348	4,850	4,668
Operating Segments | EMEA | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	52,155	62,489	94,606	101,175
Operating Segments | EMEA | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	12,492	12,425	24,560	24,434
Operating Segments | Asia Pacific | ACI On Premise
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	24,855	21,736	41,044	40,432
Operating Segments | Asia Pacific | ACI On Demand
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 2,075	$ 1,002	$ 4,076	$ 2,008