Consolidated Statement of Cash Flows (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Interest credited to deposit accounts	$ 6,903	$ 4,798

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