Allowance for Loan Losses - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2015 USD ($) Contract	Dec. 31, 2014 USD ($) Loan Contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of nonperforming loans	90 days
Non-accruing loans excluded from impaired loan	$ 95	$ 663
Non-accruing loans accrued interest	$ 5	$ 32
Subsequently defaulted number of loans \| Loan		3
Number of trouble debt restructurings \| Contract	16	14
Aggregate balance of trouble debt restructuring	$ 3,500	$ 2,500
Charge off of loan default		$ 75

Finance Receivable Trouble Debt Restructuring Amount

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing Receivable Number Of Contracts Classified As Trouble Debt Restructuring

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Amount of non accruing loans excluded from the impaired loan disclosure.

+ References

No definition available.

+ Details

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

- Definition

Period of nonperforming loans.

+ References

No definition available.

+ Details

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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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953682-111524

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the amount of the write-down related to a troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18794-111554

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration