Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Basis of presentation - The accompanying unaudited interim consolidated financial statements have been prepared pursuant to the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Accordingly, they do not include all the information and footnotes required by U.S. Generally Accepted Accounting Principles ("GAAP") for complete financial statements. These unaudited interim consolidated financial statements should be read in conjunction with our audited consolidated financial statements and accompanying notes included in the Company's Annual Report on Form 10-K for the year ended December 31, 2024. In our opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of the consolidated financial statements in accordance with GAAP have been included. Operating results for the three and six months ended June 30, 2025, are not necessarily indicative of the results that may be expected for future periods. In preparing the unaudited interim consolidated financial statements, we are required to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term relate to a determination of the allowance for credit losses ("ACL"), fair value of financial instruments and derivatives, and deferred tax assets and liabilities.
Consolidation, Policy [Policy Text Block]	Principles of consolidation - The accompanying consolidated financial statements include the accounts of First Northwest and its wholly owned subsidiary, First Fed. All material intercompany accounts and transactions have been eliminated in consolidation.
Subsequent Events, Policy [Policy Text Block]	Subsequent events - The Company has evaluated subsequent events for potential recognition and disclosure.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently adopted accounting pronouncements In March 2024, the FASB issued ASU 2024-01, Compensation—Stock Compensation (Topic 718): Scope Application of Profits Interest and Similar Awards. ASU 2024-01 added an illustrative example to demonstrate how an entity should apply the scope guidance in paragraph 718-10-15-3 to determine whether a profits interest award should be accounted for in accordance with Topic 718. Awards not meeting the criteria should be accounted for in accordance with Topic 710. The illustrative example provides four fact patterns which are intended to reduce complexity in determining whether a profits interest award is subject to the guidance in Topic 718 and reduce existing diversity in practice. ASU 2024-01 is effective for the Company for fiscal years beginning after December 15, 2024, including interim periods within those fiscal years, with early adoption permitted. The adoption of this ASU did not have a material impact on the consolidated financial statements and related disclosures. *Recently issued accounting pronouncements not* yet adopted** In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. ASU 2024-03 requires additional disclosure of the nature of expenses included in the income statement in response to requests from investors for more information to better understand an entity's performance and potential future cash flows. The new standard requires disclosures about specific types of expenses included in the expense captions presented on the face of the income statement as well as disclosures about selling expenses. ASU 2024-03 is effective for the Company for fiscal years beginning after December 15, 2026, including interim periods within those fiscal years, with early adoption permitted. The adoption of this ASU is not expected to have a material impact on the consolidated financial statements and related disclosures. In November 2024, the FASB issued ASU 2024-04, Debt—Debt with Conversion and Other Options (Subtopic 470-20): Induced Conversions of Convertible Debt Instruments. ASU 202404 clarifies the requirements for determining whether certain settlements of convertible debt instruments should be accounted for as an induced conversion. The amendments do not change the accounting for conversions that include the issuance of all equity securities upon conversion. ASU 2024-04 is effective for the Company for fiscal years beginning after December 15, 2025, including interim periods within those fiscal years, with early adoption permitted. The adoption of this ASU is not expected to have a material impact on the consolidated financial statements and related disclosures.

Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2025

Basis of Accounting, Policy [Policy Text Block]

Basis of presentation - The accompanying unaudited interim consolidated financial statements have been prepared pursuant to the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Accordingly, they do not include all the information and footnotes required by U.S. Generally Accepted Accounting Principles ("GAAP") for complete financial statements. These unaudited interim consolidated financial statements should be read in conjunction with our audited consolidated financial statements and accompanying notes included in the Company's Annual Report on Form 10-K for the year ended December 31, 2024. In our opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of the consolidated financial statements in accordance with GAAP have been included. Operating results for the three and six months ended June 30, 2025, are not necessarily indicative of the results that may be expected for future periods.

In preparing the unaudited interim consolidated financial statements, we are required to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term relate to a determination of the allowance for credit losses ("ACL"), fair value of financial instruments and derivatives, and deferred tax assets and liabilities.

Consolidation, Policy [Policy Text Block]

Principles of consolidation - The accompanying consolidated financial statements include the accounts of First Northwest and its wholly owned subsidiary, First Fed. All material intercompany accounts and transactions have been eliminated in consolidation.

Subsequent Events, Policy [Policy Text Block]

Subsequent events - The Company has evaluated subsequent events for potential recognition and disclosure.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently adopted accounting pronouncements

In March 2024, the FASB issued ASU 2024-01, Compensation—Stock Compensation (Topic 718): Scope Application of Profits Interest and Similar Awards. ASU 2024-01 added an illustrative example to demonstrate how an entity should apply the scope guidance in paragraph 718-10-15-3 to determine whether a profits interest award should be accounted for in accordance with Topic 718. Awards not meeting the criteria should be accounted for in accordance with Topic 710. The illustrative example provides four fact patterns which are intended to reduce complexity in determining whether a profits interest award is subject to the guidance in Topic 718 and reduce existing diversity in practice. ASU 2024-01 is effective for the Company for fiscal years beginning after December 15, 2024, including interim periods within those fiscal years, with early adoption permitted. The adoption of this ASU did not have a material impact on the consolidated financial statements and related disclosures.

Recently issued accounting pronouncements not yet adopted

In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. ASU 2024-03 requires additional disclosure of the nature of expenses included in the income statement in response to requests from investors for more information to better understand an entity's performance and potential future cash flows. The new standard requires disclosures about specific types of expenses included in the expense captions presented on the face of the income statement as well as disclosures about selling expenses. ASU 2024-03 is effective for the Company for fiscal years beginning after December 15, 2026, including interim periods within those fiscal years, with early adoption permitted. The adoption of this ASU is not expected to have a material impact on the consolidated financial statements and related disclosures.

In November 2024, the FASB issued ASU 2024-04, Debt—Debt with Conversion and Other Options (Subtopic 470-20): Induced Conversions of Convertible Debt Instruments. ASU 202404 clarifies the requirements for determining whether certain settlements of convertible debt instruments should be accounted for as an induced conversion. The amendments do not change the accounting for conversions that include the issuance of all equity securities upon conversion. ASU 2024-04 is effective for the Company for fiscal years beginning after December 15, 2025, including interim periods within those fiscal years, with early adoption permitted. The adoption of this ASU is not expected to have a material impact on the consolidated financial statements and related disclosures.