| Document and Entity Information | Mar. 29, 2021 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 29, 2021 |
| Entity File Number | 1-12431 |
| Entity Registrant Name | UNITY BANCORP, INC. |
| Entity Incorporation, State or Country Code | NJ |
| Entity Tax Identification Number | 22-3282551 |
| Entity Address, Address Line One | 64 Old Highway 22 |
| Entity Address, City or Town | Clinton |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 08809 |
| City Area Code | 908 |
| Local Phone Number | 730-7630 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock |
| Trading Symbol | UNTY |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000920427 |
| Amendment Flag | false |
