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Note 16 - Regulatory Matters - Summary of Company and Bank Continue to Exceed Regulatory Capital Minimum Requirements and Bank Continues to Exceed Well Capitalized Standards (Details) $ in Thousands | Sep. 30, 2020 USD ($) | Dec. 31, 2019 USD ($) | Jan. 01, 2015
--- | --- | --- | ---
Banking Regulation, Tier One Risk-Based Capital Ratio, Capital Adequacy, Minimum |  |  | 0.040
Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio |  |  | 0.060
RBB Bancorp [Member] |  |  |
Tier 1 Leverage Ratio, Amount | $ 361,290 | $ 353,572 |
Tier 1 Leverage Ratio, Ratio | 11.47 | 0.1289 |
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 125,998 | $ 109,735 |
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Ratio | 4.0 | 0.040 |
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Amount | $ 125,998 | $ 109,735 |
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Ratio | 4.00% | 4.00% |
Tier 1 Leverage Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 157,497 | $ 137,169 |
Tier 1 Leverage Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 5.0 | 0.050 |
Common Equity Tier 1 Risk-Based Capital Ratio, Amount | $ 347,061 | $ 343,899 |
Common Equity Tier 1 Risk-Based Capital Ratio, Ratio | 14.11 | 0.1716 |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 110,704 | $ 90,165 |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio | 4.50% | 4.50% |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount | $ 172,207 | $ 140,256 |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio | 0.070 | 0.070 |
Common Equity Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 159,906 | $ 130,238 |
Common Equity Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 6.50% | 6.50% |
Tier 1 Risk-Based Capital Ratio, Amount | $ 361,290 | $ 353,572 |
Tier 1 Risk-Based Capital Ratio, Ratio | 14.69 | 0.1765 |
Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 147,606 | $ 120,219 |
Banking Regulation, Tier One Risk-Based Capital Ratio, Capital Adequacy, Minimum | 6.0 | 0.060 |
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount | $ 209,108 | $ 170,311 |
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio | 8.50% | 8.50% |
Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 196,808 | $ 160,292 |
Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 8.0 | 0.080 |
Total Risk-Based Capital Ratio, Amount | $ 493,358 | $ 477,262 |
Total Risk-Based Capital Ratio, Ratio | 20.05 | 0.2382 |
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 196,808 | $ 160,292 |
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio | 8.0 | 0.080 |
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount | $ 258,310 | $ 210,384 |
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio | 10.50% | 10.50% |
Total Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 246,010 | $ 200,366 |
Total Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 10.0 | 0.100 |
Royal Business Bank [Member] |  |  |
Tier 1 Leverage Ratio, Amount | $ 445,699 | $ 417,036 |
Tier 1 Leverage Ratio, Ratio | 14.16 | 0.1523 |
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 125,929 | $ 108,150 |
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Ratio | 4.0 | 0.040 |
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Amount | $ 125,929 | $ 108,150 |
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Ratio | 4.00% | 4.00% |
Tier 1 Leverage Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 157,411 | $ 135,187 |
Tier 1 Leverage Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 5.0 | 0.050 |
Common Equity Tier 1 Risk-Based Capital Ratio, Amount | $ 445,699 | $ 417,036 |
Common Equity Tier 1 Risk-Based Capital Ratio, Ratio | 18.13 | 0.2087 |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 110,432 | $ 89,127 |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio | 4.50% | 4.50% |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount | $ 171,783 | $ 138,642 |
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio | 7.0 | 0.070 |
Common Equity Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 159,513 | $ 128,739 |
Common Equity Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 6.50% | 6.50% |
Tier 1 Risk-Based Capital Ratio, Amount | $ 445,699 | $ 417,036 |
Tier 1 Risk-Based Capital Ratio, Ratio | 18.13 | 0.2087 |
Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 147,242 | $ 118,836 |
Banking Regulation, Tier One Risk-Based Capital Ratio, Capital Adequacy, Minimum | 6.0 | 0.060 |
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount | $ 208,593 | $ 168,351 |
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio | 8.50% | 8.50% |
Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 196,323 | $ 158,448 |
Tier 1 Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 8.0 | 0.080 |
Total Risk-Based Capital Ratio, Amount | $ 473,462 | $ 436,677 |
Total Risk-Based Capital Ratio, Ratio | 19.26 | 0.2186 |
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount | $ 196,323 | $ 158,448 |
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio | 8.0 | 0.080 |
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount | $ 257,674 | $ 207,964 |
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio | 10.50% | 10.50% |
Total Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Amount | $ 245,404 | $ 198,061 |
Total Risk-Based Capital Ratio, To Be Well-Capitalized Under Prompt Corrective Provisions Ratio | 10.0 | 0.100 |

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