Segment Information Selected Segment Financial Data, Revenues and Operating Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues									$ 1,009,780	$ 1,024,191	$ 1,005,701
Depreciation and amortization expense									97,350	102,224	103,454
Stock-based compensation expense									20,360	13,683	43,613
Corporate and unallocated expenses									(92,296)	(144,715)	58,633
Interest, net									(30,388)	(38,449)	(39,654)
Other, net	$ (688)	$ (1,304)	$ (1,677)	$ (55)	$ (443)	$ (1,059)	$ (1,766)	$ 649	(3,724)	(2,619)	4,105
Income before income taxes	$ 108,744	$ 17,245	$ (10,810)	$ (23,380)	$ 98,922	$ 1,155	$ (50,723)	$ (5,782)	91,799	43,572	185,581
ACI On Premise [Member]
Segment Reporting Information [Line Items]
Revenues									576,755	598,590	591,252
ACI On Demand [Member]
Segment Reporting Information [Line Items]
Revenues									433,025	425,601	399,033
Operating Segments [Member] | ACI On Premise [Member]
Segment Reporting Information [Line Items]
Revenues									576,755	598,590	591,252
Segment Adjusted EBITDA									323,902	347,094	312,188
Depreciation and amortization expense									11,634	13,094	14,581
Stock-based compensation expense									4,348	2,234	6,894
Operating Segments [Member] | ACI On Demand [Member]
Segment Reporting Information [Line Items]
Revenues									433,025	425,601	399,033
Segment Adjusted EBITDA									12,015	(1,832)	(2,624)
Depreciation and amortization expense									31,541	34,171	29,385
Stock-based compensation expense									4,338	2,230	6,876
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues											15,416
Depreciation and amortization expense									54,175	54,959	59,488
Stock-based compensation expense									$ 11,674	$ 9,219	$ 29,843