Loans and Allowance for Credit Losses on Loans - Schedule of Financial Effect of Loan Modifications (Details)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Commercial and industrial \| Commercial and industrial \| Weighted-Average Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Weighted-Average Interest Rate Reduction	4.80%
Commercial and industrial \| Commercial and industrial \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Weighted-Average Term Extension (in years)	1 year 8 months 12 days
Commercial Real Estate Loans \| Commercial owner-occupied \| Weighted-Average Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Weighted-Average Interest Rate Reduction	0.00%
Commercial Real Estate Loans \| Commercial owner-occupied \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Weighted-Average Term Extension (in years)	6 months
Commercial Real Estate Loans \| Commercial real estate, non-owner occupied \| Weighted-Average Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Weighted-Average Interest Rate Reduction	0.00%
Commercial Real Estate Loans \| Commercial real estate, non-owner occupied \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Weighted-Average Term Extension (in years)	1 year 2 months 12 days
Residential Portfolio Segment \| Home equity \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Weighted-Average Term Extension (in years)		6 years 7 months 6 days

Bank of Marin Bancorp 10-K