| Document and Entity Information | Aug. 01, 2023 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | FISERV INC |
| Amendment Flag | true |
| Entity Central Index Key | 0000798354 |
| Document Type | 8-K/A |
| Document Period End Date | Aug. 01, 2023 |
| Entity Incorporation State 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 |
| Amendment Description | Fiserv, Inc. (the “Company”) filed a Current Report on Form 8-K on August 1, 2023 (the “Original Form 8-K”) reporting, under Item 5.02, the appointment of Charlotte Yarkoni to its board of directors. Because Ms. Yarkoni was not appointed to serve on any committee of the board of directors at the time the Original Form 8-K was filed, disclosure of the committees of the board of directors on which she would serve was not included in accordance with Instruction 2 to Item 5.02. The Company hereby amends Item 5.02 of the Original Form 8-K to include information on the committee assignments. Other than providing the additional information, no other disclosure in the Original Form 8-K is amended by this Form 8-K/A. On February 21, 2024, the board of directors of the Company appointed Ms. Yarkoni to the Audit and Risk committees of the board of directors effective as of February 21, 2024. |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, par value $0.01 per share |
| Trading Symbol | FI |
| Security Exchange Name | NYSE |
| Senior Notes Due 2027 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 1.125% Senior Notes due 2027 |
| Trading Symbol | FI27 |
| Security Exchange Name | NYSE |
| Senior Notes Due 2030 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 1.625% Senior Notes due 2030 |
| Trading Symbol | FI30 |
| Security Exchange Name | NYSE |
| Senior Notes Due 2025 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 2.250% Senior Notes due 2025 |
| Trading Symbol | FI25 |
| Security Exchange Name | NYSE |
| M 3.000 Senior Notes Due 20312 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 3.000% Senior Notes due 2031 |
| Trading Symbol | FI31 |
| Security Exchange Name | NYSE |
| M 4.500 Senior Notes Due 20311 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 4.500% Senior Notes due 2031 |
| Trading Symbol | FI31A |
| Security Exchange Name | NYSE |
