Consolidated Statement of Cash Flows (Unaudited) (Parentheticals) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Interest credited to deposit accounts	$ 3,372	$ 2,050

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

No definition available.

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