Note 11 - Benefit Plans (Details Textual)	12 Months Ended
	Dec. 31, 2025 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) shares	Dec. 31, 2023 USD ($)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit), Period (Year)		15 years
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Cost	$ 554,000	$ 543,000
Employee Stock Ownership Plan (ESOP), Minimum Service Period, Hours	1,000
Employee Stock Ownership Plan (ESOP), Requisite Service Period (Month)	12 months
Employee Stock Ownership Plan (ESOP), Shares to be Purchased, Percentage	8.00%
Employee Stock Ownership Plan (ESOP), Shares in ESOP, Total (in shares) | shares	1,048,029	1,048,029
Employee Stock Ownership Plan (ESOP), Number of Shares Purchased, Percentage	100.00%
Employee Stock Ownership Plan (ESOP), Weighted Average Purchase Price of Shares Purchased (in dollars per share) | $ / shares	$ 12.45
Employee Stock Ownership Plan (ESOP), Debt Structure, Amortization Period (Year)	20 years
Employee Stock Ownership Plan (ESOP), Debt Structure, Estimated Interest Rate	2.46%
Employee Stock Ownership Plan (ESOP), Principal and Interest Payments from ESOP	$ 835,000	$ 837,000
Employee Stock Ownership Plan (ESOP), Compensation Expense, Net of Dividends Received	$ 376,000	$ 353,000
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | shares	184,901
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 1,100,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	2 years 2 months 12 days
First Northwest Bancorp 2020 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares) | shares	520,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares) | shares	95,789
First Northwest Bancorp 2020 Equity Incentive Plan [Member] | Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | shares	151,650	81,181
First Northwest Bancorp 2020 Equity Incentive Plan [Member] | Restricted Stock [Member] | Minimum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)	1 year
First Northwest Bancorp 2020 Equity Incentive Plan [Member] | Restricted Stock [Member] | Maximum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)	5 years
First Northwest Bancorp 2020 Equity Incentive Plan [Member] | Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | shares	33,251	0
First Northwest Bancorp 2015 Equity Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares) | shares	0
First Northwest Bancorp 2015 and 2020 Equity Incentive Plan [Member]
Share-Based Payment Arrangement, Expense	$ 733,000	$ 957,000
Board of Directors and Officers [Member]
Deferred Compensation Arrangement with Individual, Aggregate Balance Held in Trust	1,400,000
Director [Member] | First Northwest Bancorp 2015 and 2020 Equity Incentive Plan [Member]
Share-Based Payment Arrangement, Expense	248,000	242,000
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Equity, Attributable to Parent	$ (1,184,000)	$ (1,303,000)	$ (1,421,000)