v3.26.1
Note 17 - 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
Jun. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
RBB Bancorp [Member]    
Tier 1 Leverage Ratio, Amount $ 492,367 $ 479,047
Tier 1 Leverage Ratio, Ratio 0.1186 0.116
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 166,128 $ 165,193
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 0.04 0.04
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Amount $ 207,661 $ 206,491
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Ratio 5.00% 5.00%
Common Equity Tier 1 Risk-Based Capital Ratio, Amount $ 477,348 $ 464,133
Common Equity Tier 1 Risk-Based Capital Ratio, Ratio 0.18 0.1749
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 119,327 $ 119,388
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 4.50% 4.50%
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount $ 172,361 $ 172,450
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio 0.065 0.065
Tier 1 Risk-Based Capital Ratio, Amount $ 492,367 $ 479,047
Tier 1 Risk-Based Capital Ratio, Ratio 0.1857 0.1806
Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 159,102 $ 159,184
Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 0.06 0.06
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount $ 212,136 $ 212,246
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio 8.00% 8.00%
Total Risk-Based Capital Ratio, Amount $ 621,648 $ 632,260
Total Risk-Based Capital Ratio, Ratio 0.2344 0.2383
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 212,136 $ 212,246
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 0.08 0.08
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount $ 265,171 $ 265,307
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio 10.00% 10.00%
Royal Business Bank [Member]    
Tier 1 Leverage Ratio, Amount $ 520,358 $ 544,296
Tier 1 Leverage Ratio, Ratio 0.1254 0.132
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 165,918 $ 164,965
Tier 1 Leverage Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 0.04 0.04
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Amount $ 207,398 $ 206,206
Tier 1 Leverage Ratio, Minimum Required Plus Capital Conservation Buffer Fully Phased-In Ratio 5.00% 5.00%
Common Equity Tier 1 Risk-Based Capital Ratio, Amount $ 520,358 $ 544,296
Common Equity Tier 1 Risk-Based Capital Ratio, Ratio 0.1968 0.2057
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 118,988 $ 119,075
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 4.50% 4.50%
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount $ 171,872 $ 171,998
Common Equity Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio 0.065 0.065
Tier 1 Risk-Based Capital Ratio, Amount $ 520,358 $ 544,296
Tier 1 Risk-Based Capital Ratio, Ratio 0.1968 0.2057
Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 158,651 $ 158,767
Tier 1 Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 0.06 0.06
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount $ 211,535 $ 211,690
Tier 1 Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio 8.00% 8.00%
Total Risk-Based Capital Ratio, Amount $ 553,546 $ 577,512
Total Risk-Based Capital Ratio, Ratio 0.2093 0.2182
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Amount $ 211,535 $ 211,690
Total Risk-Based Capital Ratio, Minimum Required for Capital Adequacy Purposes Ratio [1] 0.08 0.08
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Amount $ 264,418 $ 264,612
Total Risk-Based Capital Ratio, Minimum Required Plus Capital Conversation Buffer Fully Phased-In, Ratio 10.00% 10.00%
[1] These ratios are exclusive of the 2.5% capital conservation buffer.