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, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
OPERATING ACTIVITIES:
Net income	$ 9,956,000	$ 9,942,000	$ 9,451,000	$ 9,108,000	$ 9,746,000	$ 9,459,000	$ 8,418,000	$ 8,496,000	$ 7,345,000	$ 5,760,000	$ 5,171,000	$ 5,368,000	$ 38,457,000	$ 36,119,000	$ 23,644,000
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of securities													1,313,000	(609,000)	(93,000)
Net cash provided by operating activities													42,669,000	32,529,000	22,323,000
INVESTING ACTIVITIES
Purchase of land and building													(1,482,000)	(1,249,000)	(559,000)
Purchases of securities													(2,539,000)	(6,100,000)	0
Net cash used in investing activities													(541,283,000)	(40,515,000)	(175,362,000)
FINANCING ACTIVITIES
Proceeds from exercise of stock options													1,698,357	630,302	451,420
Purchase of treasury stock													(42,000)	(4,191,000)	(7,442,000)
Cash dividends on common stock													(4,373,000)	(3,617,000)	(3,298,000)
Net cash provided by financing activities													368,589,000	33,493,000	214,334,000
Increase (decrease) in cash and cash equivalents													(130,025,000)	25,507,000	61,295,000
Cash and cash equivalents, beginning of period				244,818,000				219,311,000				158,016,000	244,818,000	219,311,000	158,016,000
Cash and cash equivalents, end of period	114,793,000				244,818,000				219,311,000				114,793,000	244,818,000	219,311,000
Parent Company Only | Reportable Legal Entities
OPERATING ACTIVITIES:
Net income													38,457,000	36,119,000	23,644,000
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries													(33,368,000)	(23,621,000)	(15,231,000)
Gain on sales of securities													0	(4,000)	(5,000)
Net change in other assets and other liabilities													153,000	(472,000)	507,000
Net cash provided by operating activities													5,242,000	12,022,000	8,915,000
INVESTING ACTIVITIES
Purchase of land and building													0	0	(87,000)
Purchases of securities													(1,539,000)	(3,500,000)	0
Proceeds from sales of securities													0	53,000	111,000
Net cash used in investing activities													(1,539,000)	(3,447,000)	24,000
FINANCING ACTIVITIES
Proceeds from exercise of stock options													1,357,000	379,000	229,000
Repayment of advances from subsidiaries													(105,000)	(101,000)	(96,000)
Purchase of treasury stock													(42,000)	(4,191,000)	(7,442,000)
Cash dividends on common stock													(4,373,000)	(3,617,000)	(3,298,000)
Net cash provided by financing activities													(3,163,000)	(7,530,000)	(10,607,000)
Increase (decrease) in cash and cash equivalents													540,000	1,045,000	(1,668,000)
Cash and cash equivalents, beginning of period				$ 1,685,000				$ 640,000				$ 2,308,000	1,685,000	640,000	2,308,000
Cash and cash equivalents, end of period	$ 2,225,000				$ 1,685,000				$ 640,000				2,225,000	1,685,000	640,000
SUPPLEMENTAL DISCLOSURES
Interest paid													$ 436,000	$ 361,000	$ 458,000