Name:	rbkb_DepositsLineItems
Namespace Prefix:	rbkb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the amount of reciprocal deposits included in money market accounts.

No definition available.

Name:	rbkb_MoneyMarketAccountsReciprocalDeposits
Namespace Prefix:	rbkb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the amount of reciprocal deposits.

No definition available.

Name:	rbkb_ReciprocalDeposits
Namespace Prefix:	rbkb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of reciprocal deposits included in time deposit liabilities.

No definition available.

Name:	rbkb_TimeDepositsReciprocalDeposits
Namespace Prefix:	rbkb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of interest-bearing domestic third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

Name:	us-gaap_InterestBearingDomesticDepositBrokered
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Period of time between issuance and maturity of customer deposits, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Industry Guide
-Number 3
-Section V
-Paragraph D-E
-Publisher SEC

Name:	us-gaap_MaturityOfTimeDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

Amount of time deposit liabilities, including certificates of deposit, in denominations that meet or exceed the Federal Deposit Insurance Corporation (FDIC) insurance limit.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-SubTopic 405
-Topic 942
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481047/942-405-50-1