Selected Segment Financial Data, Revenues and Long lived Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 209,310	$ 231,462
Long lived assets
Long lived assets	1,573,766		$ 1,373,069
Bill Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	66,168	65,246
Digital Channels/Online [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	22,007	22,979
Merchant Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	17,381	17,671
Payments Risk Management [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	22,218	15,468
Real Time Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	14,091	13,743
Retail Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	67,445	96,355
ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	105,030	131,908
ACI On Premise [Member] | Digital Channels/Online [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	11,363	12,488
ACI On Premise [Member] | Merchant Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	5,010	6,312
ACI On Premise [Member] | Payments Risk Management [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	10,420	5,160
ACI On Premise [Member] | Real Time Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	13,641	13,548
ACI On Premise [Member] | Retail Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	64,596	94,400
ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	104,280	99,554
ACI On Demand [Member] | Bill Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	66,168	65,246
ACI On Demand [Member] | Digital Channels/Online [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	10,644	10,491
ACI On Demand [Member] | Merchant Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	12,371	11,359
ACI On Demand [Member] | Payments Risk Management [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	11,798	10,308
ACI On Demand [Member] | Real Time Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	450	195
ACI On Demand [Member] | Retail Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	2,849	1,955
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	119,810	135,002
Long lived assets
Long lived assets	854,156		759,513
United States [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	30,864	49,193
United States [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	88,946	85,809
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	19,103	17,126
Long lived assets
Long lived assets	719,610		$ 613,556
Other [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	16,784	14,874
Other [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	2,319	2,252
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	50,695	62,983
EMEA [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	38,686	51,904
EMEA [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	12,009	11,079
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	19,702	16,351
Asia Pacific [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	18,696	15,937
Asia Pacific [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,006	$ 414