Note 11 - Junior Subordinated Debentures (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Junior Subordinated Notes, Total	$ 10,310	$ 10,310
Bank of Commerce Holdings Trust II [Member]
Common Stock Held in Trust	$ 310	$ 310
Junior Subordinated Debt [Member] \| Bank of Commerce Holdings Trust II [Member]
Debt Instrument, Basis Spread on Variable Rate	1.58%
Debt Instrument, Interest Rate, Effective Percentage	1.80%	3.47%
Junior Subordinated Notes, Total	$ 10,310

Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16)(a))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Name:	us-gaap_JuniorSubordinatedNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant