Accumulated amortized cost excluding accrued interest, of financing receivable modified for debtor experiencing financial difficulty.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestModifiedAccumulated
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PaymentDeferralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityAndInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=rbb_PrincipalReductionExtendedMaturityAndInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=rbb_CommercialAndIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=rbb_SBALoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=rbb_ConstructionAndLandDevelopmentLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetNotPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=rbb_FinancialAsset30To89DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LOANS AND ALLOWANCE FOR CREDIT LOSSES - Schedule of Loan Modifications (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Financing Receivable, Modified [Line Items]
Total Loan Modifications	$ 3,899	$ 5,282	$ 5,199	$ 13,523
Loan Class	5,199	51,947	5,199	51,947
Term Extension
Financing Receivable, Modified [Line Items]
Total Loan Modifications	3,899		4,562
Payment Deferral
Financing Receivable, Modified [Line Items]
Total Loan Modifications		5,282	637	5,282
Combination - Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				4,709
Combination - Principal Reduction, Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				3,532
Commercial real estate
Financing Receivable, Modified [Line Items]
Total Loan Modifications		$ 4,872	$ 663	$ 8,404
% of Loan Class		0.38%	0.05%	0.65%
Loan Class	663	$ 18,607	$ 663	$ 18,607
Commercial real estate \| Term Extension
Financing Receivable, Modified [Line Items]
Total Loan Modifications			663
Commercial real estate \| Payment Deferral
Financing Receivable, Modified [Line Items]
Total Loan Modifications		4,872	0	4,872
Commercial real estate \| Combination - Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				0
Commercial real estate \| Combination - Principal Reduction, Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				3,532
Commercial and industrial
Financing Receivable, Modified [Line Items]
Total Loan Modifications	$ 3,899		$ 3,899	$ 4,709
% of Loan Class	2.57%		2.57%	3.21%
Loan Class	$ 3,899	4,708	$ 3,899	$ 4,708
Commercial and industrial \| Term Extension
Financing Receivable, Modified [Line Items]
Total Loan Modifications	3,899		3,899
Commercial and industrial \| Payment Deferral
Financing Receivable, Modified [Line Items]
Total Loan Modifications			0	0
Commercial and industrial \| Combination - Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				4,709
Commercial and industrial \| Combination - Principal Reduction, Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				0
SBA
Financing Receivable, Modified [Line Items]
Total Loan Modifications		$ 410	$ 637	$ 410
% of Loan Class		0.76%	1.31%	0.76%
Loan Class	637	$ 410	$ 637	$ 410
SBA \| Term Extension
Financing Receivable, Modified [Line Items]
Total Loan Modifications			0
SBA \| Payment Deferral
Financing Receivable, Modified [Line Items]
Total Loan Modifications		410	637	410
SBA \| Combination - Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				0
SBA \| Combination - Principal Reduction, Rate Reduction and Term Modification
Financing Receivable, Modified [Line Items]
Total Loan Modifications				0
Construction and land development
Financing Receivable, Modified [Line Items]
Loan Class		28,222		28,222
Current
Financing Receivable, Modified [Line Items]
Loan Class	5,199	23,725	5,199	23,725
Current \| Commercial real estate
Financing Receivable, Modified [Line Items]
Loan Class	663	18,607	663	18,607
Current \| Commercial and industrial
Financing Receivable, Modified [Line Items]
Loan Class	3,899	4,708	3,899	4,708
Current \| SBA
Financing Receivable, Modified [Line Items]
Loan Class	637	410	637	410
Current \| Construction and land development
Financing Receivable, Modified [Line Items]
Loan Class		0		0
30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan Class	0	0	0	0
30-89 Days Past Due \| Commercial real estate
Financing Receivable, Modified [Line Items]
Loan Class	0	0	0	0
30-89 Days Past Due \| Commercial and industrial
Financing Receivable, Modified [Line Items]
Loan Class	0	0	0	0
30-89 Days Past Due \| SBA
Financing Receivable, Modified [Line Items]
Loan Class	0	0	0	0
30-89 Days Past Due \| Construction and land development
Financing Receivable, Modified [Line Items]
Loan Class		0		0
90 Days or More
Financing Receivable, Modified [Line Items]
Loan Class	0	28,222	0	28,222
90 Days or More \| Commercial real estate
Financing Receivable, Modified [Line Items]
Loan Class	0	0	0	0
90 Days or More \| Commercial and industrial
Financing Receivable, Modified [Line Items]
Loan Class	0	0	0	0
90 Days or More \| SBA
Financing Receivable, Modified [Line Items]
Loan Class	$ 0	0	$ 0	0
90 Days or More \| Construction and land development
Financing Receivable, Modified [Line Items]
Loan Class		$ 28,222		$ 28,222