Cover Page
| Cover Page | Apr. 27, 2021 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Apr. 27, 2021 |
| Entity Registrant Name | Fiserv, Inc. |
| Entity Incorporation, State or Country Code | WI |
| Entity File Number | 1-38962 |
| Entity Tax Identification Number | 39-1506125 |
| Entity Address, Address Line One | 255 Fiserv Drive |
| Entity Address, City or Town | Brookfield |
| Entity Address, State or Province | WI |
| Entity Address, Postal Zip Code | 53045 |
| City Area Code | 262 |
| Local Phone Number | 879-5000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000798354 |
| Amendment Flag | false |
| Common Stock, par value $0.01 per share | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | FISV |
| Security Exchange Name | NASDAQ |
| 0.375% Senior Notes due 2023 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 0.375% Senior Notes due 2023 |
| Trading Symbol | FISV23 |
| Security Exchange Name | NASDAQ |
| 1.125% Senior Notes due 2027 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 1.125% Senior Notes due 2027 |
| Trading Symbol | FISV27 |
| Security Exchange Name | NASDAQ |
| 1.625% Senior Notes due 2030 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 1.625% Senior Notes due 2030 |
| Trading Symbol | FISV30 |
| Security Exchange Name | NASDAQ |
| 2.250% Senior Notes due 2025 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 2.250% Senior Notes due 2025 |
| Trading Symbol | FISV25 |
| Security Exchange Name | NASDAQ |
| 3.000% Senior Notes due 2031 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 3.000% Senior Notes due 2031 |
| Trading Symbol | FISV31 |
| Security Exchange Name | NASDAQ |