Condensed Financial Statements of Unity Bancorp, Inc. (Parent Company Only) - Condensed Statements of Cash Flows (Details) - USD ($)	3 Months Ended												12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES:
Net income	$ 6,120,000	$ 5,959,000	$ 5,834,000	$ 5,740,000	$ 5,803,000	$ 5,490,000	$ 5,397,000	$ 5,229,000	$ 2,500,000	$ 3,757,000	$ 3,444,000	$ 3,192,000	$ 23,653,000	$ 21,919,000	$ 12,893,000
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of securities													(373,000)	199,000	(62,000)
INVESTING ACTIVITIES
Purchase of land and building													(709,000)	(1,507,000)	(1,509,000)
Purchases of securities													0	(1,133,000)	0
FINANCING ACTIVITIES
Proceeds from exercise of stock options													453,326	576,119	509,047
Dividends on common stock													(3,255,000)	(2,802,000)	(2,380,000)
Increase (decrease) in cash and cash equivalents													12,501,000	(4,739,000)	44,359,000
Cash and cash equivalents, beginning of year				145,515,000				150,254,000				105,895,000	145,515,000	150,254,000	105,895,000
Cash and cash equivalents, end of year	158,016,000				145,515,000				150,254,000				158,016,000	145,515,000	150,254,000
Parent Company Only
OPERATING ACTIVITIES:
Net income													23,653,000	21,919,000	12,893,000
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiary													(20,284,000)	(19,273,000)	(10,515,000)
Gain on sales of securities													(17,000)	0	0
Net change in other assets and other liabilities													506,000	377,000	(81,000)
Net cash provided by operating activities													3,858,000	3,023,000	2,297,000
INVESTING ACTIVITIES
Purchase of land and building													(64,000)	0	(55,000)
Purchases of securities													0	(1,133,000)	(262,000)
Proceeds from sales of securities													198,000	0	0
Net cash provided by (used in) investing activities													134,000	(1,133,000)	(317,000)
FINANCING ACTIVITIES
Proceeds from exercise of stock options													453,000	576,000	509,000
Repayment of advances from subsidiaries													(91,000)	(87,000)	(83,000)
Dividends on common stock													(3,255,000)	(2,802,000)	(2,380,000)
Net cash used in financing activities													(2,893,000)	(2,313,000)	(1,954,000)
Increase (decrease) in cash and cash equivalents													1,099,000	(423,000)	26,000
Cash and cash equivalents, beginning of year				$ 1,209,000				$ 1,632,000				$ 1,606,000	1,209,000	1,632,000	1,606,000
Cash and cash equivalents, end of year	$ 2,308,000				$ 1,209,000				$ 1,632,000				2,308,000	1,209,000	1,632,000
SUPPLEMENTAL DISCLOSURES
Interest paid													$ 479,000	$ 368,000	$ 374,000