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Organization and Nature of Business and Summary of Significant Accounting Policies (Branches) (Details)	Dec. 31, 2025 Bank_branches
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

X

- Definition

The number of bank branches in a particular location.

+ References

No definition available.

+ Details

Name:	wtba_NumberOfBankBranches
Namespace Prefix:	wtba_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

[Line Items] for Schedule of locations of bank branches [Table]

+ References

No definition available.

+ Details

Name:	wtba_ScheduleOfLocationsOfBankBranchesLineItems
Namespace Prefix:	wtba_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- 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:

X

- Details

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