Cash Reserves - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Federal Reserve	$ 11.2	$ 13.5

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