Document and Entity Information	9 Months Ended
	Sep. 30, 2011	Oct. 25, 2011
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q3
Trading Symbol	ACIW
Entity Registrant Name	ACI WORLDWIDE, INC.
Entity Central Index Key	0000935036
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		33,503,529