Revenue under New Operating Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	$ 326,395	$ 225,735	$ 240,599	$ 231,462	$ 342,730	$ 216,975	$ 219,930	$ 226,066	$ 1,024,191	$ 1,005,701	$ 1,045,977
Operating Segments [Member] | ACI On Premise [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues									598,590	591,252	589,006
Operating Segments [Member] | ACI On Demand [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues									$ 425,601	399,033	362,368
Corporate and Other [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues										$ 15,416	$ 94,603