Securities - Securities Pledged to Secure Public Deposits and for Other Purposes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Securities Pledged to Secure Public Deposits and for Other Purposes
Amortized cost of securities pledged to secure public deposits and for other purposes as required or permitted by law or contract	$ 110,874	$ 135,023

The amortized cost of available-for-sale securities that serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

No definition available.

Name:	htbk_AvailableForSaleSecuritiesPledgedAsCollateralAmortizedCost
Namespace Prefix:	htbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant