Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 28, 2022	Jun. 30, 2021
Document and Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 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
Title of 12(b) Security	Common stock
Trading Symbol	UNTY
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		10,458,418
Entity Central Index Key	0000920427
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
ICFR Auditor Attestation Flag	false
Entity Public Float			$ 165,265,842
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Auditor Name	RSM US LLP
Auditor Firm ID	49
Auditor Location	New York, New York