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Note 10 - Stock-based Compensation (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	May 31, 2020
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	8,894		106,588
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 1,400,000		$ 1,400,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			2 years 2 months 12 days
Restricted Stock [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			1 year
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]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)					520,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)	120,377		120,377
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)			73,337	68,138
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)			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)	0		0
The Equity Incentive Plans [Member]
Share-Based Payment Arrangement, Expense	$ 211,000	$ 257,000	$ 405,000	$ 521,000
The Equity Incentive Plans [Member] \| Director [Member]
Share-Based Payment Arrangement, Expense	$ 65,000	$ 56,000	$ 121,000	$ 110,000