| Document and Entity Information | Jun. 17, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | HORIZON BANCORP INC /IN/ |
| Amendment Flag | false |
| Entity Central Index Key | 0000706129 |
| Document Type | 8-K |
| Document Period End Date | Jun. 17, 2020 |
| Entity Incorporation State 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 |
| Security 12b Title | Common stock, no par value |
| Trading Symbol | HBNC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
