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Business and Summary of Significant Accounting Policies - Nature of business (Details) | 12 Months Ended
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Dec. 31, 2024 Item
Chicago metropolitan area |
Nature of business |
Number of bank branches | 45
Wisconsin |
Nature of business |
Number of bank branches | 1

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- References No definition available. + Details
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Namespace Prefix: | by_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the number of bank branches. + References No definition available. + Details
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Namespace Prefix: | by_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_StatementGeographicalAxis=by_ChicagoMetropolitanAreaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_StatementGeographicalAxis=stpr_WI
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |