Income Taxes - Components of Net Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets
Allowance for loan losses	$ 661	$ 632
Interest on non-accrual loans	47	40
Mortgage servicing rights		197
Other real estate	397bayk_DeferredTaxAssetsOtherRealEstate	477bayk_DeferredTaxAssetsOtherRealEstate
Pension plan	222
Postretirement benefits	262	206
Deferred compensation	141	114
Stock-based compensation	25	18
Alternative minimum tax credit		96
Unrealized losses on available-for-sale securities		408
Other	11us-gaap_DeferredTaxAssetsOther	3us-gaap_DeferredTaxAssetsOther
Total deferred tax assets	1,766us-gaap_DeferredTaxAssetsGross	2,191us-gaap_DeferredTaxAssetsGross
Deferred tax liabilities
Unrealized gains on available-for-sale securities	(23)
Pension plan		(27)
Depreciation	(218)bayk_DeferredTaxLiabilitiesDepreciation	(276)bayk_DeferredTaxLiabilitiesDepreciation
Amortization of goodwill	(928)	(896)
Net deferred loan fees and costs	(134)	(172)
Other	(67)us-gaap_DeferredTaxLiabilitiesOther	(64)us-gaap_DeferredTaxLiabilitiesOther
Total deferred tax (liabilities)	(1,370)us-gaap_DeferredIncomeTaxLiabilities	(1,435)us-gaap_DeferredIncomeTaxLiabilities
Net deferred tax assets	$ 396us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 756us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred Tax Assets Mortgage Servicing Rights

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Deferred tax assets other real estate.

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Deferred tax assets tax deferred expense deferred compensation.

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Deferred tax assets tax deferred expense reserves and accruals interest on nonaccrual loans.

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Deferred Tax Liabilities, Acquired Goodwill Amortization

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Deferred tax liabilities depreciation.

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Deferred Tax Liabilities, Pension Benefits

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Deferred tax liabilities unrealized losses on available for sale securities gross.

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences not separately disclosed.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible alternative minimum tax credit carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from pension benefits.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from postretirement benefits.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from the provision for loan losses.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from unrealized losses on available-for-sale securities.

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Amount of deferred tax liability attributable to taxable temporary differences from deferred financing costs.

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Amount of deferred tax liability attributable to taxable temporary differences not separately disclosed.

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