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Organization and Nature of Business and Summary of Significant Accounting Policies (Branches) (Details) | Dec. 31, 2025 Bank_branches
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Des Moines, Iowa metropolitan area, excluding main [Member] |
Number of bank branches by location [Line Items] |
Number of bank branches | 5
Coralville, Iowa [Member] |
Number of bank branches by location [Line Items] |
Number of bank branches | 1
Minnesota |
Number of bank branches by location [Line Items] |
Number of bank branches | 4

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- Definition The number of bank branches in a particular location. + References No definition available. + Details
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Namespace Prefix: | wtba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition [Line Items] for Schedule of locations of bank branches [Table] + References No definition available. + Details
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Namespace Prefix: | wtba_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | wtba_LocationsOfBankBranchesAxis=wtba_DesMoinesIowaMetropolitanAreaExcludingMainMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wtba_LocationsOfBankBranchesAxis=wtba_CoralvilleIowaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | wtba_LocationsOfBankBranchesAxis=stpr_MN
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |