Regulatory Matters - Schedule of Compliance with Regulatory Capital Requirements (Details) $ in Thousands	Jun. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Regulated Operations [Abstract]
Tier 1 Leverage ratio, Actual amount	$ 150,618	$ 147,851
Tier 1 Leverage ratio, Actual ratio	0.1713	0.1644
Tier 1 capital (to risk-weighted assets), Actual amount	$ 150,618	$ 147,851
Tier 1 capital (to risk-weighted assets), Actual ratio	0.224	0.2113
Common Equity Tier 1 Capital Ratio (to risk-weighted assets), Actual amount	$ 150,618	$ 147,851
Common Equity Tier 1 Capital Ratio (to risk-weighted assets), Actual ratio	0.224	0.2113
Total Capital ratio (to risk-weighted assets), Actual amount	$ 156,959	$ 154,386
Total Capital ratio (to risk-weighted assets), Actual ratio	0.2334	0.2206
Tier 1 Leverage ratio, For capital adequacy purposes amount	$ 35,168	$ 35,976
Tier 1 Leverage ratio, For capital adequacy purposes ratio	0.04	0.04
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes amount	$ 40,351	$ 41,989
Tier 1 capital (to risk-weighted assets), For capital adequacy purposes ratio	0.06	0.06
Common Equity Tier 1 Capital Ratio (to risk-weighted assets), For capital adequacy purposes amount	$ 30,263	$ 31,492
Common Equity Tier 1 Capital Ratio (to risk-weighted assets), For capital adequacy purposes ratio	0.045	0.045
Total Capital ratio (to risk-weighted assets), For capital adequacy purposes amount	$ 53,802	$ 55,986
Total Capital ratio (to risk-weighted assets), For capital adequacy purposes ratio	0.08	0.08
Tier 1 Leverage ratio, Well Capitalized amount	$ 43,960	$ 44,970
Tier 1 Leverage ratio, Well Capitalized ratio	0.05	0.05
Tier 1 capital (to risk-weighted assets), Well Capitalized ratio	$ 53,802	$ 55,986
Tier 1 capital (to risk-weighted assets), Well Capitalized ratio	0.08	0.08
Common Equity Tier 1 Capital Ratio (to risk-weighted assets), Well Capitalized amount	$ 43,714	$ 45,488
Common Equity Tier 1 Capital Ratio (to risk-weighted assets), Well Capitalized ratio	0.065	0.065
Total Capital ratio (to risk-weighted assets), Well Capitalized amount	$ 67,252	$ 69,982
Total Capital ratio (to risk-weighted assets), Well Capitalized ratio	0.10	0.10

Tier one risk based capital required for capital adequacy with buffer.

No definition available.

Name:	bvfl_TierOneRiskBasedCapitalRequiredForCapitalAdequacyWithBuffer
Namespace Prefix:	bvfl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Tier one risk based capital required for capital adequacy with buffer to risk weighted assets.

+ References

No definition available.

+ Details

Name:	bvfl_TierOneRiskBasedCapitalRequiredForCapitalAdequacyWithBufferToRiskWeightedAssets
Namespace Prefix:	bvfl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of minimum Common Equity Tier 1 risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

+ Details

Name:	us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioCapitalAdequacyMinimum
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of minimum Common Equity Tier 1 risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

+ Details

Name:	us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioWellCapitalizedMinimum
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of total capital as defined by regulatory framework.

+ References

+ Details

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

- Definition

Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

+ References

+ Details

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

- Definition

Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of minimum total risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

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

- Definition

Ratio of minimum total risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of total risk-based capital to risk-weighted assets as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_CapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of Common Equity Tier 1 risk-based capital as defined by regulatory framework.

+ References

+ Details

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

- Definition

Ratio of Common Equity Tier 1 risk-based capital to risk-weighted assets as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_CommonEquityTierOneCapitalRatio
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of minimum Common Equity Tier 1 risk-based capital required for capital adequacy as defined by regulatory framework.

+ References

+ Details

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

- Definition

Amount of minimum Common Equity Tier 1 risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of Tier 1 leverage capital as defined by regulatory framework.

+ References

+ Details

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

- Definition

Amount of minimum Tier 1 leverage capital required for capital adequacy as defined by regulatory framework.

+ References

+ Details

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

- Definition

Ratio of minimum Tier 1 leverage capital to average assets required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of minimum Tier 1 leverage capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

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

- Definition

Ratio of minimum Tier 1 leverage capital to average assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of Tier 1 capital to average assets as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of Tier 1 risk-based capital as defined by regulatory framework.

+ References

+ Details

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

- Definition

Amount of minimum Tier 1 risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

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

- Definition

Ratio of minimum Tier 1 risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of Tier 1 risk-based capital to risk-weighted assets as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant