Condensed Consolidated Financial Statements - Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Goodwill [Line Items]
Gross Balance prior to the end of year		$ 957,123
Total impairment, beginning of period		(47,432)
Beginning Balance	$ 909,691
Adjustments	0
Ending Balance	909,691
ACI On Demand [Member]
Goodwill [Line Items]
Gross Balance prior to the end of year		183,783
Total impairment, beginning of period		0
Beginning Balance	183,783
Adjustments	0
Ending Balance	183,783
ACI On Premise [Member]
Goodwill [Line Items]
Gross Balance prior to the end of year		773,340
Total impairment, beginning of period		$ (47,432)
Beginning Balance	725,908
Adjustments	0
Ending Balance	$ 725,908