Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited consolidated financial statements and corresponding footnotes have been prepared by Northrim BanCorp, Inc. (the “Company”) in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and with instructions to Form 10-Q under the Securities Exchange Act of 1934, as amended. The year-end Consolidated Balance Sheet data was derived from the Company's audited financial statements. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The Company owns a 100% interest in Residential Mortgage Holding Company, LLC, the parent company of Residential Mortgage, LLC (collectively "RML") and consolidates their balance sheets and income statement into its financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. The Company determined that it operates in two primary operating segments: Community Banking and Home Mortgage Lending. The Company has evaluated subsequent events and transactions for potential recognition or disclosure. Operating results for the interim period ended September 30, 2023 are not necessarily indicative of the results anticipated for the year ending December 31, 2023. These consolidated financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2022.
Reclassification of Prior Period Presentation	Reclassification of Prior Period Presentation Certain prior year amounts have been reclassified for consistency with the current period presentation. These reclassifications had no effect on the reported results of operations or total shareholders' equity.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting pronouncements implemented in 2023 In March 2022, the FASB issued ASU 2022-02, Financial Instruments - Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures ("ASU 2022-02"). The amendments in ASU 2022-02 eliminate the accounting guidance for troubled debt restructurings ("TDRs") by creditors while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty. Specifically, rather than applying the recognition and measurement guidance for TDRs which includes an assessment of whether the creditor has granted a concession, an entity must evaluate whether the modification represents a new loan or a continuation of an existing loan. The amendments enhance existing disclosure requirements and introduce new requirements related to certain modifications of receivables made to borrowers experiencing financial difficulty. Additionally, for public business entities, ASU 2022-02 requires that an entity disclose current-period gross writeoffs by year of origination for financing receivables and net investments in leases within the scope of Subtopic 326-20, Financial Instruments-Credit Losses-Measured at Amortized Cost in the vintage disclosures required by paragraph 326-20-50-6. The Company adopted ASU 2022-02 on January 1, 2023. The Company elected to adopt the updated guidance on TDR recognition and measurement prospectively; therefore the guidance is applied to modifications occurring after the date of adoption. The amendments on TDR disclosures and vintage disclosures must be adopted prospectively. The adoption of ASU 2022-02 did not have a material impact on the Company's consolidated financial position or results of operations. Accounting pronouncements to be implemented in future periods In March 2023, the FASB issued ASU 2023-02, Investments - Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Tax Credit Structures Using the Proportional Amortization Method ("ASU 2023-02"). Under current GAAP, an entity can only elect to apply the proportional amortization method to investments in low income housing tax credit ("LIHTC") structures. The amendments in ASU 2023-02 allow entities to elect to account for equity investments made primarily for the purpose of receiving income tax credits using the proportional amortization method, regardless of the tax credit program through which the investment earns income tax credits, if certain conditions are met. ASU 2023-02 provides amendments to paragraph ASC 323-740-25-1, which sets forth the conditions needed to apply the proportional amortization method. The amendments make certain limited changes to those conditions to clarify their application to a broader group of tax credit investment programs. However, the conditions in substance remain consistent with current GAAP. The amendments in this ASU 2023-02 also eliminate certain LIHTC-specific guidance to align the accounting more closely for LIHTCs with the accounting for other equity investments in tax credit structures and require that the delayed equity contribution guidance in paragraph ASC 323-740-25-3 applies only to tax equity investments accounted for using the proportional amortization method. ASU 2023-02 is effective for the Company for fiscal years beginning after December 15, 2023 and must be applied on either a modified retrospective or a retrospective basis. The Company does not have any equity investments made primarily for the purpose of receiving income tax credits except for LIHTC structures, which it accounts for using the proportional amortization method. The Company does not believe that the adoption of ASU 2023-02 will have a material impact on the Company's consolidated financial statements.