Note 20 - Regulatory Capital - Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Common Equity Tier One Risk Based Capital Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Subtotal Bank of Commerce Holdings [Member]
Common Equity Tier One Risk Based Capital	$ 125,745	$ 92,757
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	12.26%	9.43%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 46,169	$ 44,266
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	1.25%	0.625%
Common Equity Tier One, Capital Adequacy Plus Capital Conservation Buffer	$ 58,994	$ 50,414
Common Equity Tier One Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	5.75%	5.125%
Tier 1 capital ratio	$ 135,745	$ 102,496
Tier One Risk Based Capital to Risk Weighted Assets	13.23%	10.42%
Tier One Risk Based Capital Required for Capital Adequacy	$ 61,559	$ 59,021
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	1.25%	0.625%
Tier One Risk Based Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 74,384	$ 65,169
Tier One Risk Based Capital Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	7.25%	6.625%
Capital	$ 158,365	$ 124,735
Capital to Risk Weighted Assets	15.44%	12.68%
Capital Required for Capital Adequacy	$ 82,079	$ 78,695
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Applicable capital conservation buffer, Total capital ratio	1.25%	0.625%
Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 94,903	$ 84,843
Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	9.25%	8.625%
Tier One Leverage Capital	$ 135,745	$ 102,496
Tier One Leverage Capital to Average Assets	10.86%	9.13%
Tier One Leverage Capital Required for Capital Adequacy	$ 50,008	$ 44,905
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Commercial Banking [Member]
Common Equity Tier One Risk Based Capital	$ 129,139	$ 121,098
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	12.58%	12.31%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 46,179	$ 44,281
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	1.25%	0.625%
Common Equity Tier One, Capital Adequacy Plus Capital Conservation Buffer	$ 59,006	$ 50,432
Common Equity Tier One Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	5.75%	5.125%
Tier 1 capital ratio	$ 129,139	$ 121,098
Tier One Risk Based Capital to Risk Weighted Assets	12.58%	12.31%
Tier One Risk Based Capital Required for Capital Adequacy	$ 61,572	$ 59,042
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	1.25%	0.625%
Tier One Risk Based Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 74,399	$ 65,192
Tier One Risk Based Capital Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	7.25%	6.625%
Capital	$ 141,760	$ 133,337
Capital to Risk Weighted Assets	13.81%	13.55%
Capital Required for Capital Adequacy	$ 82,096	$ 78,722
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Applicable capital conservation buffer, Total capital ratio	1.25%	0.625%
Capital Required to be Well Capitalized, Capital Adequacy Plus Capital Conservation Buffer	$ 94,923	$ 84,873
Capital Adequacy Plus Capital Conservation Buffer to Risk Weighted Assets	9.25%	8.625%
Tier One Leverage Capital	$ 129,139	$ 121,098
Tier One Leverage Capital to Average Assets	10.33%	10.80%
Tier One Leverage Capital Required for Capital Adequacy	$ 49,989	$ 44,835
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized	$ 66,703	$ 63,962
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	$ 82,096	$ 78,722
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Capital Required to be Well Capitalized	$ 102,620	$ 98,403
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 62,486	$ 56,043
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%