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
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(12))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-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.

No definition available.

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/1943274/2147478353/942-405-50-1