Organization and Presentation - Additional Information (Detail)	12 Months Ended
Dec. 31, 2016 Subsidiary
Organization And Basis Of Presentation [Line Items]
Number of active subsidiaries	2

Organization And Basis Of Presentation [Line Items]

No definition available.

Name:	bayk_OrganizationAndBasisOfPresentationLineItems
Namespace Prefix:	bayk_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration