Equity Plan - Stock Option Activity (Details) - Options - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019
Number of Shares
Outstanding at the beginning of the period (in shares)	1,570,603
Granted (in shares)	299,500
Heritage Commerce Corp stock options	2,712,846	2,712,846
Exercised (in shares)	(266,689)
Forfeited or expired (in shares)	(67,325)
Outstanding at the end of the period (in shares)	2,712,846
Vested or expected to vest (in shares)		2,550,075
Exercisable at the end of the period (in shares)		2,206,775
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 10.76
Granted (in dollars per share)	12.16
Heritage Commerce Corp stock options	8.80	$ 8.80
Exercised (in dollars per share)	6.10
Forfeited or expired (in dollars per share)	14.31
Outstanding at the end of the period (in dollars per share)	$ 8.80
Additional Information
Weighted Average Remaining Contractual Life - Outstanding at the end of the period (in years)	5 years 7 months 13 days
Weighted Average Remaining Contractual Life - Vested or expected to vest (in years)	5 years 7 months 13 days
Weighted Average Remaining Contractual Life - Exercisable at the end of the period (in years)	4 years 11 months 5 days
Aggregate Intrinsic Value - Outstanding at the end of the period (in dollars)		$ 12,369,413
Aggregate Intrinsic Value - Vested or expected to vest (in dollars)		11,627,248
Aggregate Intrinsic Value - Exercisable at the end of the period (in dollars)		$ 12,151,054
Presidio bank
Number of Shares
Heritage Commerce Corp stock options	1,176,757	1,176,757
Outstanding at the end of the period (in shares)	1,176,757
Weighted Average Exercise Price
Heritage Commerce Corp stock options	$ 5.05	$ 5.05
Outstanding at the end of the period (in dollars per share)	$ 5.05