Document and Entity Information
| Document and Entity Information | Jul. 23, 2021 |
| Cover [Abstract] | |
| Security Exchange Name | NASDAQ |
| Amendment Flag | false |
| Entity Central Index Key | 0000944745 |
| Document Type | 8-K |
| Document Period End Date | Jul. 23, 2021 |
| Entity Registrant Name | Civista Bancshares, Inc. |
| Entity Incorporation State Country Code | OH |
| Entity File Number | 001-36192 |
| Entity Tax Identification Number | 34-1558688 |
| Entity Address, Address Line One | 100 East Water Street |
| Entity Address, Address Line Two | P.O. Box 5016 |
| Entity Address, City or Town | Sandusky |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 44870 |
| City Area Code | (419) |
| Local Phone Number | 625-4121 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common |
| Trading Symbol | CIVB |
| Entity Emerging Growth Company | false |