CONSOLIDATED STATEMENT OF CASH FLOWS (UNAUDITED) (Parentheticals) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Statement of Cash Flows [Abstract]
Interest credit to deposit accounts	$ 4,382	$ 5,070

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