Conditional age one for availing other post retirement benefit plan.

No definition available.

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

- Definition

Conditional age two for availing other post retirement benefit plan.

+ References

No definition available.

+ Details

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

- Definition

Conditional years of service one for availing other post retirement benefit plan.

+ References

No definition available.

+ Details

Name:	bayk_ConditionalYearsOfServiceOneForAvailingOtherPostRetirementBenefitPlan
Namespace Prefix:	bayk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Conditional years of service two for availing other post retirement benefit plan.

+ References

No definition available.

+ Details

Name:	bayk_ConditionalYearsOfServiceTwoForAvailingOtherPostRetirementBenefitPlan
Namespace Prefix:	bayk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Obligation Maximum Contractual Period

+ References

No definition available.

+ Details

Name:	bayk_DefinedBenefitObligationMaximumContractualPeriod
Namespace Prefix:	bayk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined benefit plan health care cost trend rate assumed in fifth year and thereafter.

+ References

No definition available.

+ Details

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

- Definition

Defined benefit plan health care cost trend rate assumed in four years.

+ References

No definition available.

+ Details

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

- Definition

Defined benefit plan health care cost trend rate assumed in three years.

+ References

No definition available.

+ Details

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

- Definition

Defined benefit plan health care cost trend rate assumed in two years.

+ References

No definition available.

+ Details

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

- Definition

For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6503844

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before tax, after reclassification adjustments, of actuarial gain (loss) that has not been recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580

+ Details

Name:	us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

+ Details

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

- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

+ Details

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

- Definition

The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (l)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Health Care Cost Trend Rate

-URI http://asc.fasb.org/extlink&oid=6514820

+ Details

Name:	us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

+ Details

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

- Definition

Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e2446-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=bayk_FourZeroOneRetirementPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_EquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2014 Age	Mar. 09, 2015	Dec. 31, 2013
Defined Contribution Plan Disclosure [Line Items]
Conditional age-1 for availing plan	55
Conditional age-2 for availing plan	65
Conditional years of service -1 for availing plan	10 years
Conditional years of service-2 for availing plan	5 years
Discount rate assumption	5.00%		4.00%
Subsequent Event \| First 3% of Each Participant's Contributions
Defined Contribution Plan Disclosure [Line Items]
Matching contribution to defined contribution plan		100.00%
Percentage of employee's contributions		3.00%
Subsequent Event \| Second 3% of Each Participant's Contributions
Defined Contribution Plan Disclosure [Line Items]
Matching contribution to defined contribution plan		50.00%
Percentage of employee's contributions		3.00%
Fixed Income Funds
Defined Contribution Plan Disclosure [Line Items]
Targeted asset allocation percentage	40.00%
Equity Funds
Defined Contribution Plan Disclosure [Line Items]
Targeted asset allocation percentage	60.00%
Four Zero One Retirement Plan
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	110,000		$ 97,000
Conditional period of service for availing plan	6 months
Four Zero One Retirement Plan \| First 2% of Each Participant's Contributions
Defined Contribution Plan Disclosure [Line Items]
Matching contribution to defined contribution plan	100.00%
Percentage of employee's contributions	2.00%
Four Zero One Retirement Plan \| Second 4% of Each Participant's Contributions
Defined Contribution Plan Disclosure [Line Items]
Matching contribution to defined contribution plan	25.00%
Percentage of employee's contributions	4.00%
Pension Plan, Defined Benefit
Defined Contribution Plan Disclosure [Line Items]
Net loss	(755,000)		224,000
Accumulated benefit obligation	3,500,000		2,700,000
Expected employer contribution	0
Other Postretirement Benefit Plan, Defined Benefit
Defined Contribution Plan Disclosure [Line Items]
Net loss	(130,000)		194,000
Expected employer contribution	22,435
Assumed annual rate of increase in per capita health care costs in 2015	8.00%
Assumed annual rate of increase in per capita health care costs in 2016	8.00%
Assumed annual rate of increase in per capita health care costs in 2017	6.00%
Assumed annual rate of increase in per capita health care costs in 2018	6.00%
Assumed annual rate of increase in per capita health care costs,2019 and thereafter	5.00%
Accumulated postretirement benefit obligation at assumed health care cost trend rates increased by 1 percentage	893
Aggregate of the service and interest cost components at assumed health care cost trend rates increased by 1 percentage	39
Accumulated postretirement benefit obligation at assumed health care cost trend rates decreased by 1 percentage	838
Aggregate of the service and interest cost components at assumed health care cost trend rates decreased by 1 percentage	36
Employer contributions	11,000		$ 15,000