| Document and Entity Information | Nov. 05, 2019 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0000935036 |
| Document Type | 8-K |
| Document Period End Date | Nov. 5, 2019 |
| Entity Registrant Name | ACI WORLDWIDE, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 0-25346 |
| Entity Tax Identification Number | 47-0772104 |
| Entity Address, Address Line One | 3520 Kraft Rd |
| Entity Address, Address Line Two | Suite 300 |
| Entity Address, City or Town | Naples |
| Entity Address, State or Province | FL |
| Entity Address, Postal Zip Code | 34105 |
| City Area Code | (239) |
| Local Phone Number | 403-4600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.005 par value |
| Trading Symbol | ACIW |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
