Employee Stock Ownership Plan - Additional Information (Detail)	12 Months Ended
Dec. 31, 2015 USD ($) Age shares	Dec. 31, 2014 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Noncontributory employee stock ownership plan, service period eligibility	12 months
Noncontributory employee stock ownership plan, age eligibility \| Age	21
Allocations, as a percentage of eligible participant compensation	25.00%
Participant accounts vested after two years	30.00%
Participant accounts vested after three years	40.00%
Participant accounts vested each year, from fourth year till 100% vested	20.00%
Participant accounts, total vested	100.00%
Allocated shares \| shares	122,522
Contributions to the plan	$ 50,000	$ 3,000
Dividends on the company's stock held by the ESOP	$ 0	$ 0

Employee Stock Ownership Plan Esop Allocation Percentage

No definition available.

Name:	bayk_EmployeeStockOwnershipPlanEsopAllocationPercentage
Namespace Prefix:	bayk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Employee Stock Ownership Plan Esop Minimum Age Qualification

+ References

No definition available.

+ Details

Name:	bayk_EmployeeStockOwnershipPlanEsopMinimumAgeQualification
Namespace Prefix:	bayk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Employee Stock Ownership Plan Esop Participant Accounts Vested After Three Years Percentage

+ References

No definition available.

+ Details

Name:	bayk_EmployeeStockOwnershipPlanEsopParticipantAccountsVestedAfterThreeYearsPercentage
Namespace Prefix:	bayk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Employee Stock Ownership Plan Esop Participant Accounts Vested After Two Years Percentage

+ References

No definition available.

+ Details

Name:	bayk_EmployeeStockOwnershipPlanEsopParticipantAccountsVestedAfterTwoYearsPercentage
Namespace Prefix:	bayk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Employee Stock Ownership Plan Esop Participant Accounts Vested Each Year From Fourth Year Till Hundred Percentage Vested Percentage

+ References

No definition available.

+ Details

Name:	bayk_EmployeeStockOwnershipPlanEsopParticipantAccountsVestedEachYearFromFourthYearTillHundredPercentageVestedPercentage
Namespace Prefix:	bayk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Employee Stock Ownership Plan Esop Participant Accounts Vested Percentage

+ References

No definition available.

+ Details

Name:	bayk_EmployeeStockOwnershipPlanEsopParticipantAccountsVestedPercentage
Namespace Prefix:	bayk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents the amount of cash contributions during the period made by the entity to the Employee Stock Ownership Plan (ESOP).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPCashContributionsToESOP
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Dividends paid on stock held by an employee stock ownership plan.

+ References

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPDividendsPaidToESOP
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The shares or units in an ESOP trust that have been assigned to individual participant accounts based on a known formula. IRS rules require allocations to be nondiscriminatory generally based on compensation, length of service, or a combination of both. For any particular participant such shares or units may be vested, unvested, or partially vested.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration