Name:	bwb_DeferredTaxAssetsReserveForUnfundedLoanCommitments
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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from unrealized gain on cash flow hedge.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from unrealized losses (gains) on available-for-sale securities.

No definition available.

Name:	bwb_DeferredTaxAssetsUnrealizedLossesGainsOnAvailableForSaleSecuritiesGross
Namespace Prefix:	bwb_
Data Type:	xbrli:monetaryItemType
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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred income.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-6

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-8

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Data Type:	xbrli:monetaryItemType
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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-2

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Data Type:	xbrli:monetaryItemType
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- References

No definition available.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences, classified as other.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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

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Data Type:	xbrli:monetaryItemType
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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary difference from allowance for credit loss on financing receivable.

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Data Type:	xbrli:monetaryItemType
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Amount of deferred tax consequences attributable to taxable temporary differences derived from prepaid expenses.

No definition available.

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

Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.