Segment Information Selected Segment Financial Data, Revenues and Long lived Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,009,780	$ 1,024,191	$ 1,005,701
Long lived assets
Long lived assets	1,528,930	1,373,069
Bill Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	275,526	271,421	255,540
Digital Channels [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	75,573	94,036	124,630
Merchant Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	89,942	76,953	64,626
Payment Intelligence [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	89,144	80,326	67,649
Real Time Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	94,261	72,872	70,994
Retail Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	385,334	428,583	422,262
ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	576,755	598,590	591,252
ACI On Premise [Member] | Digital Channels [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	35,231	47,973	49,617
ACI On Premise [Member] | Merchant Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	30,153	26,430	29,311
ACI On Premise [Member] | Payment Intelligence [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	42,647	33,203	24,665
ACI On Premise [Member] | Real Time Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	92,068	70,087	70,289
ACI On Premise [Member] | Retail Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	376,656	420,897	417,370
ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	433,025	425,601	399,033
ACI On Demand [Member] | Bill Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	275,526	271,421	255,540
ACI On Demand [Member] | Digital Channels [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	40,342	46,063	59,597
ACI On Demand [Member] | Merchant Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	59,789	50,523	35,315
ACI On Demand [Member] | Payment Intelligence [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	46,497	47,123	42,984
ACI On Demand [Member] | Real Time Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	2,193	2,785	705
ACI On Demand [Member] | Retail Payments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	8,678	7,686	4,892
Corporate and Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues			15,416
Corporate and Other [Member] | Digital Channels [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues			15,416
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	500,479	541,235	527,431
Long lived assets
Long lived assets	811,435	759,513
United States [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	131,382	175,682	164,058
United States [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	369,097	365,553	347,957
United States [Member] | Corporate and Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues			15,416
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	71,546	82,231	116,718
Long lived assets
Long lived assets	717,495	613,556
Other [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	61,969	72,802	110,463
Other [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	9,577	9,429	6,255
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	345,046	318,260	261,160
EMEA [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	296,157	270,388	217,576
EMEA [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	48,889	47,872	43,584
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	92,709	82,465	100,392
Asia Pacific [Member] | ACI On Premise [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	87,247	79,718	99,155
Asia Pacific [Member] | ACI On Demand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 5,462	$ 2,747	$ 1,237