Loans Receivable and Allowance for Loan Losses (Unpaid Principal Balance and Related Recorded Investment of Acquired Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Loans Receivable and Allowance for Loan Losses [Abstract]
Unpaid principle balance	$ 214,773	$ 226,333
Recorded investment	$ 183,208	$ 192,826

Value as of the balance sheet date of the unpaid principal balances of acquired loans.

No definition available.

Name:	bcbp_AcquiredLoansUnpaidPrincipalBalance
Namespace Prefix:	bcbp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant