Value of input used to measure collateral dependent loans.

No definition available.

Name:	rbb_CollateralDependentLoansMeasurementInput
Namespace Prefix:	rbb_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The buy price on derivative.

+ References

No definition available.

+ Details

Name:	rbb_DerivativeBuyPrice
Namespace Prefix:	rbb_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

The sale price of derivative.

+ References

No definition available.

+ Details

Name:	rbb_DerivativeSalePrice
Namespace Prefix:	rbb_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of write-down related to collateral dependent loans.

+ References

No definition available.

+ Details

Name:	rbb_FinancingReceivablesCollateralDependentWritedown
Namespace Prefix:	rbb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents write down on other real estate owned.

+ References

No definition available.

+ Details

Name:	rbb_WriteDownOnOtherRealEstateOwned
Namespace Prefix:	rbb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Value of input used to measure alternative investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_AlternativeInvestmentMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

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

- Definition

Value of input used to measure derivative asset.

+ References

+ Details

Name:	us-gaap_DerivativeAssetMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The net gain (loss) resulting from sales and other disposals of other real estate owned, increases (decreases) in the valuation allowance for foreclosed real estate, and write-downs of other real estate owned after acquisition or physical possession.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Name:	us-gaap_GainsLossesOnSalesOfOtherRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Publisher FASB
-URI https://asc.fasb.org//310-10/tableOfContent

+ Details

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

- Definition

Disposals of other real estate not separately disclosed, including, but not limited to, real estate investments, real estate loans that qualify as investments in real estate, and premises that are no longer used in operations may also be included in real estate owned. This excludes real estate assets taken in settlement of troubled loans through surrender or foreclosure.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherRealEstateDisposals
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=rbb_InterestRateLockContractsAndForwardMortgageLoanSaleContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=rbb_SinglefamilyResidencesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=rbb_MeasurementInputSellingCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputComparabilityAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rbb_OtherRealEstateOwnedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=rbb_MeasurementInputMarginCostRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=us-gaap_CollateralPledgedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 18 - Fair Value Measurements and Fair Value of Financial Instruments (Details Textual)			12 Months Ended
	Nov. 10, 2023 USD ($)	Sep. 01, 2023 USD ($)	Dec. 31, 2023 USD ($) $ / item	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Financing Receivables, Collateral Dependent, Write-down			$ 521,000
Other Real Estate, Disposals	$ 284,000	$ 293,000
Gains (Losses) on Sales of Other Real Estate	$ (57,000)	$ 190,000	134,000	$ (0)	$ (0)
Write Down on Other Real Estate Owned			$ 0	0
Minimum [Member] \| Interest Rate Lock Contracts and Forward Mortgage Loan Sale Contracts [Member]
Derivative, Buy Price (in USD per Per Share) \| $ / item			99.5
Derivative, Sale Price (in USD per Per Share) \| $ / item			102
Maximum [Member] \| Interest Rate Lock Contracts and Forward Mortgage Loan Sale Contracts [Member]
Derivative, Buy Price (in USD per Per Share) \| $ / item			100.3
Derivative, Sale Price (in USD per Per Share) \| $ / item			104
Single-Family Residences [Member]
Assets, Fair Value Disclosure			$ 0	$ 577,000
Measurement Input, Selling Costs [Member]
Collateral Dependent Loans, Measurement Input			0.10
Measurement Input, Comparability Adjustment [Member] \| Other Real Estate Owned [Member] \| Minimum [Member]
Alternative Investment, Measurement Input			0.05
Measurement Input, Comparability Adjustment [Member] \| Other Real Estate Owned [Member] \| Maximum [Member]
Alternative Investment, Measurement Input			0.06
Measurement Input, Margin Cost Rate [Member] \| Minimum [Member] \| Interest Rate Lock Contracts and Forward Mortgage Loan Sale Contracts [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivative Asset, Measurement Input			0.005
Measurement Input, Margin Cost Rate [Member] \| Maximum [Member] \| Interest Rate Lock Contracts and Forward Mortgage Loan Sale Contracts [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivative Asset, Measurement Input			1
Collateral Pledged [Member]
Loans Receivable, Fair Value Disclosure			$ 11,400,000