Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
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 March 31, 2022 are not necessarily indicative of the results anticipated for the year ending December 31, 2022. 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, 2021.
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 to be implemented in future periods In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Report of Financial Reporting ("ASU 2020-04"). ASU 2020-04 was issued to provide temporary optional guidance to ease the potential burden in accounting for reference rate reform. The guidance provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference London Inter-Bank Offered Rate ("LIBOR") or another reference rate expected to be discontinued. The last expedient is a one-time election to sell or transfer debt securities classified as held to maturity. The expedients are in effect from March 12, 2020, through December 31, 2022. The Company will be able to use the expedients in this guidance to manage through the transition away from LIBOR, specifically for our loan portfolio, derivative contracts, and bond portfolio. In January 2021, the FASB issued ASU No. 2021-01, Reference Rate Reform (Topic 848): Scope, ("ASU 2021-01"). The amendments in ASU 2021-01 are elective and apply to all entities that have derivative instruments that use an interest rate for margining, discounting, or contract price alignment that is modified as a result of reference rate reform. The amendments clarify certain optional expedients and exceptions in Topic 848 for contract modifications apply to derivatives that are affected by the discounting transition. LIBOR is a widely-referenced benchmark rate, which is published in five currencies and a range of tenors, and seeks to estimate the cost at which banks can borrow on an unsecured basis from other banks. The administrator of LIBOR, ICE Benchmark Administration, ceased the publication of one-week and two-month LIBOR, as well as all non-US Dollar LIBOR tenors as of January 1, 2022. 1-month, 3-month, 6-month, and 12-month US Dollar LIBOR will continue to be published through and will remain available for use in legacy contracts or as otherwise enumerated by financial regulators until June 30, 2023. The Company has some assets and liabilities referenced to 1-month, 3-month, and 12-month US Dollar LIBOR, such as commercial loans, derivatives, debt securities, and junior subordinated debentures. As of March 31, 2022, we had approximately $180.5 million of assets, including $102.4 million in commercial loans and $78.1 million in debt securities, and $10.0 million of liabilities in the form of our junior subordinated debentures linked to USD LIBOR. These amounts exclude derivative assets and liabilities on our consolidated balance sheet. As of March 31, 2022, the notional amount of our USD LIBOR-linked interest rate derivative contracts was $151.6 million. Of this amount, $70.8 million in notional value represent commercial loan interest rate swap agreements with commercial banking customers. An additional $70.8 million in notional value represent corresponding swap agreements with third party financial institutions that offset the commercial loan swaps. Swap agreements with third party institutions are $80.8 million, including an interest rate swap agreement for $10.0 million in notional value related to our junior subordinated debentures. Each of the USD LIBOR-linked amounts referenced above are expected to vary in future periods as current contracts expire with potential replacement contracts using an alternative reference rate. In an effort to mitigate the risks associated with a transition away from LIBOR, our Asset Liability Committee has undertaken initiatives to: (i) develop more robust fallback language and disclosures related to the LIBOR transition, (ii) develop a plan to seek to amend legacy contracts to reference such fallback language or alternative reference rates, (iii) enhance systems to support commercial loans, securities, and derivatives linked to the Secured Overnight Financing Rate and other alternative reference rates, (iv) develop and evaluate internal guidance, policies and procedures focused on the transition away from LIBOR to alternative reference rate products, and (v) prepare and disseminate internal and external communications regarding the LIBOR transition. ASU 2021-01 does not have a material impact on the Company's consolidated financial statements. 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. ASU 2022-02 is effective for the Company for fiscal years beginning after December 15, 2022. The Company may elect to apply the updated guidance on TDR recognition and measurement by using a modified retrospective transition method, which would result in a cumulative-effect adjustment to retained earnings, or to adopt the amendments prospectively. The Company intends to elect to adopt the updated guidance on TDR recognition and measurement prospectively; therefore the guidance will be applied to modifications occurring after the date of adoption. The amendments on TDR disclosures and vintage disclosures must be adopted prospectively. The Company does not believe that ASU 2022-02 will have a material impact on the Company's consolidated financial statements.