Note 17 - Regulatory Capital - Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Subtotal Bank of Commerce Holdings [Member]
Common Equity Tier One Risk Based Capital	$ 156,587	$ 139,488
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	13.19%	12.79%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 53,409	$ 49,072
Common Equity Tier One Risk Based Capital Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Applicable capital conservation buffer, common equity tier 1 capital	2.50%	1.875%
Common Equity Tier One, Capital Adequacy Plus Capital Conservation Buffer	$ 83,081	$ 69,519
Common Equity Tier One Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	7.00%	6.375%
Tier 1 capital ratio	$ 166,587	$ 149,488
Tier One Risk Based Capital to Risk Weighted Assets	14.04%	13.71%
Tier One Risk Based Capital Required for Capital Adequacy	$ 71,212	$ 65,429
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Applicable capital conservation buffer, Tier 1 capital ratio	2.50%	1.875%
Tier One Risk Based Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 100,884	$ 85,876
Tier One Risk Based Capital Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	8.50%	7.875%
Capital	$ 189,513	$ 172,475
Capital to Risk Weighted Assets	15.97%	15.82%
Capital Required for Capital Adequacy	$ 94,949	$ 87,239
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Applicable capital conservation buffer, Total capital ratio	2.50%	1.875%
Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 124,621	$ 107,686
Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	10.50%	9.875%
Tier One Leverage Capital	$ 166,587	$ 149,488
Tier One Leverage Capital to Average Assets	11.30%	11.21%
Tier One Leverage Capital Required for Capital Adequacy	$ 58,945	$ 53,079
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage, Capital Adequacy Plus Capital Conservation Buffer	$ 58,945	$ 53,079
Tier One Leverage, Capital Adequacy Plus Capital Conservative Buffer to Risk Weighted Assets	4.00%	4.00%
Commercial Banking [Member]
Common Equity Tier One Risk Based Capital	$ 170,568	$ 144,245
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	14.39%	13.23%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 53,358	$ 49,054
Common Equity Tier One Risk Based Capital Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Applicable capital conservation buffer, common equity tier 1 capital	2.50%	1.875%
Common Equity Tier One, Capital Adequacy Plus Capital Conservation Buffer	$ 83,001	$ 69,493
Common Equity Tier One Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	7.00%	6.375%
Tier 1 capital ratio	$ 170,568	$ 144,245
Tier One Risk Based Capital to Risk Weighted Assets	14.39%	13.23%
Tier One Risk Based Capital Required for Capital Adequacy	$ 71,144	$ 65,405
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Applicable capital conservation buffer, Tier 1 capital ratio	2.50%	1.875%
Tier One Risk Based Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 100,787	$ 85,844
Tier One Risk Based Capital Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	8.50%	7.875%
Capital	$ 183,494	$ 157,232
Capital to Risk Weighted Assets	15.48%	14.42%
Capital Required for Capital Adequacy	$ 94,858	$ 87,207
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Applicable capital conservation buffer, Total capital ratio	2.50%	1.875%
Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 124,502	$ 107,646
Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	10.50%	9.875%
Tier One Leverage Capital	$ 170,568	$ 144,245
Tier One Leverage Capital to Average Assets	11.58%	10.81%
Tier One Leverage Capital Required for Capital Adequacy	$ 58,917	$ 53,369
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage, Capital Adequacy Plus Capital Conservation Buffer	$ 58,917	$ 53,369
Tier One Leverage, Capital Adequacy Plus Capital Conservative Buffer to Risk Weighted Assets	4.00%	4.00%
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized	$ 77,072	$ 70,856
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier One Risk Based Capital Required to be Well Capitalized	$ 94,858	$ 87,207
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Capital Required to be Well Capitalized	$ 118,573	$ 109,009
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 73,646	$ 66,712
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%