Restrictions on Cash Due From Banks - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Federal Reserve	$ 25bayk_FederalReserveBankCashReserve	$ 25bayk_FederalReserveBankCashReserve

Daily average cash required reserve by the Federal Reserve.

No definition available.

Name:	bayk_FederalReserveBankCashReserve
Namespace Prefix:	bayk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant