| Document and Entity Information | Oct. 23, 2019 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 23, 2019 |
| Entity Registrant Name | Horizon Bancorp, Inc. |
| Entity Incorporation, State or Country Code | IN |
| Entity File Number | 000-10792 |
| Entity Tax Identification Number | 35-1562417 |
| Entity Address, Address Line One | 515 FRANKLIN STREET |
| Entity Address, City or Town | MICHIGAN CITY |
| Entity Address, State or Province | IN |
| Entity Address, Postal Zip Code | 46360 |
| City Area Code | 219 |
| Local Phone Number | 879-0211 |
| 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 | 0000706129 |
| Title of 12(b) Security | Common stock, no par value |
| Trading Symbol | HBNC |
| Security Exchange Name | NASDAQ |
