Schedule H - Line 4(i) - Schedule of Assets 2 (Details) - EBP 94-2156203 002 [Member]	12 Months Ended
Dec. 31, 2025 USD ($)
Investment, Identifier [Axis]: NotesReceivableFromPlanParticipantsMember
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution	$ 628,711
Investment, Identifier [Axis]: NotesReceivableFromPlanParticipantsMember \| Minimum [Member]
EBP, Asset Held for Investment, Participant Loan, Interest Rate	4.25%
Investment, Identifier [Axis]: NotesReceivableFromPlanParticipantsMember \| Maximum [Member]
EBP, Asset Held for Investment, Participant Loan, Interest Rate	9.75%
EBP, Asset Held for Investment, Participant Loan, Maturity Date	Dec. 30, 2030
Investment, Identifier [Axis]: VanguardCashReservesFederalMoneyMarketFundAdmiralShares
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 3,538,797
Investment, Identifier [Axis]: VanguardExplorerFundAdmiralSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 288,160
Investment, Identifier [Axis]: VanguardExtendedMarketIndexFundAdmiralSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 1,773,859
Investment, Identifier [Axis]: VanguardInstlIndexFundInstitutionalSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 13,535,483
Investment, Identifier [Axis]: VanguardShortTermBondIndexFundAdmiralSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 536,756
Investment, Identifier [Axis]: VanguardTargetRetirement2020FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 691,680
Investment, Identifier [Axis]: VanguardTargetRetirement2025FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 4,789,261
Investment, Identifier [Axis]: VanguardTargetRetirement2030FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 2,439,479
Investment, Identifier [Axis]: VanguardTargetRetirement2035FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 2,997,614
Investment, Identifier [Axis]: VanguardTargetRetirement2040FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 653,957
Investment, Identifier [Axis]: VanguardTargetRetirement2045FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 2,005,409
Investment, Identifier [Axis]: VanguardTargetRetirement2050FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 891,875
Investment, Identifier [Axis]: VanguardTargetRetirement2055FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 589,797
Investment, Identifier [Axis]: VanguardTargetRetirement2060FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 895,565
Investment, Identifier [Axis]: VanguardTargetRetirement2065FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 233,630
Investment, Identifier [Axis]: VanguardTargetRetirement2070FundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 28,013
Investment, Identifier [Axis]: VanguardTargetRetirementIncomeFundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 3,940,742
Investment, Identifier [Axis]: VanguardTotalBondMarketIndexFundAdmiralSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 2,244,779
Investment, Identifier [Axis]: VanguardTotalInternationalStockIndexFundAdmiralSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 1,547,474
Investment, Identifier [Axis]: VanguardUSGrowthFundAdmiralSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 6,976,822
Investment, Identifier [Axis]: VanguardWindsorIIFundAdmiralSharesMember
EBP, Investment, Issuer Name [Extensible Enumeration]	The Vanguard Group, Inc [Member]
The Vanguard Group, Inc.	Mutual Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 1,692,984
Investment, Identifier [Axis]: WestamericaCommonStockFundMember
EBP, Investment, Issuer Name [Extensible Enumeration]	Westamerica Bancorporation [Member]
The Vanguard Group, Inc.	EBP, Employer, Common Stock Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration]	EBP, Participant-Directed [Member]
Assets, current value	$ 13,535,278

Current value of investment, excluding plan interest in master trust, in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(D)
-Publisher DOL-EBSA

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Indicates status of participation by participant for investment, excluding plan interest in master trust, in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustParticipationStatusExtensibleEnumeration
Namespace Prefix:	us-gaap-ebp_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after deemed distribution, of participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Indicates name of issuer of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(A)
-Publisher DOL-EBSA

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (2)(i)(A)
-Publisher DOL-EBSA

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 6
-Paragraph d
-Subparagraph (1)(i)
-Publisher DOL-EBSA

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanInvestmentIssuerNameExtensibleEnumeration
Namespace Prefix:	us-gaap-ebp_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates type of investment at current value held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanInvestmentTypeExtensibleEnumeration
Namespace Prefix:	us-gaap-ebp_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Definition

Interest rate on participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maturity date of participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), in YYYY-MM-DD format.

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanParticipantLoanMaturityDate
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration