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, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES:
Net income	$ 9,746,000	$ 9,459,000	$ 8,418,000	$ 8,496,000	$ 7,345,000	$ 5,760,000	$ 5,171,000	$ 5,368,000	$ 6,120,000	$ 5,959,000	$ 5,834,000	$ 5,740,000	$ 36,119,000	$ 23,644,000	$ 23,653,000
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of securities													(609,000)	(93,000)	(373,000)
INVESTING ACTIVITIES
Purchase of land and building													(1,269,000)	(559,000)	(709,000)
Purchases of securities													(6,100,000)	0	0
FINANCING ACTIVITIES
Proceeds from exercise of stock options													630,302	451,420	453,326
Purchase of treasury stock													(4,191,000)	(7,442,000)
Dividends on common stock													(3,617,000)	(3,298,000)	(3,255,000)
Increase (decrease) in cash and cash equivalents													25,507,000	61,295,000	12,501,000
Cash and cash equivalents, beginning of period				219,311,000				158,016,000				145,515,000	219,311,000	158,016,000	145,515,000
Cash and cash equivalents, end of period	244,818,000				219,311,000				158,016,000				244,818,000	219,311,000	158,016,000
Parent Company Only | Reportable Legal Entities
OPERATING ACTIVITIES:
Net income													36,119,000	23,644,000	23,653,000
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiary													(23,621,000)	(15,231,000)	(20,284,000)
Gain on sales of securities													(4,000)	(5,000)	(17,000)
Net change in other assets and other liabilities													(723,000)	285,000	506,000
Net cash provided by operating activities													11,771,000	8,693,000	3,858,000
INVESTING ACTIVITIES
Purchase of land and building													0	(87,000)	(64,000)
Purchases of securities													(3,500,000)	0	0
Proceeds from sales of securities													53,000	111,000	198,000
Net cash provided by (used in) investing activities													(3,447,000)	24,000	134,000
FINANCING ACTIVITIES
Proceeds from exercise of stock options													630,000	451,000	453,000
Repayment of advances from subsidiaries													(101,000)	(96,000)	(91,000)
Purchase of treasury stock													(4,191,000)	(7,442,000)
Dividends on common stock													(3,617,000)	(3,298,000)	(3,255,000)
Net cash used in financing activities													(7,279,000)	(10,385,000)	(2,893,000)
Increase (decrease) in cash and cash equivalents													1,045,000	(1,668,000)	1,099,000
Cash and cash equivalents, beginning of period				$ 640,000				$ 2,308,000				$ 1,209,000	640,000	2,308,000	1,209,000
Cash and cash equivalents, end of period	$ 1,685,000				$ 640,000				$ 2,308,000				1,685,000	640,000	2,308,000
SUPPLEMENTAL DISCLOSURES
Interest paid													$ 361,000	$ 458,000	$ 479,000