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

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Number of allocated shares held by the Employee Stock Option Plan at balance sheet date. Allocated shares are shares that have been assigned to individual participant accounts based on a known formula.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

Name:	us-gaap_SharesHeldInEmployeeStockOptionPlanAllocated
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Defined contribution plan employer matching and discretionary contribution amounts.

No definition available.

Name:	wtba_DefinedContributionPlanEmployerContributionAmount
Namespace Prefix:	wtba_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Defined contribution plan, employer discretionary contribution, percentage of salaries.

No definition available.