CONSOLIDATED STATEMENT OF CASH FLOWS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020
Statement of Cash Flows [Abstract]
Interest credit to deposit accounts	$ 1,916	$ 3,104

The amount of cash paid for interest credited to deposit accounts during the period.

No definition available.

Name:	cbfv_InterestExpenseAndAccruedInterestOnDepositAccounts
Namespace Prefix:	cbfv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration