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Note 10 - Stock-based Compensation (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	May 31, 2026	May 31, 2020
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	10,820		66,966
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 1,000,000		$ 1,000,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			1 year 10 months 24 days
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	10,820	72,538	50,921	145,875
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)					820,000	520,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)	344,732		344,732
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)	0	0	16,045	33,251
The Equity Incentive Plans [Member]
Share-Based Payment Arrangement, Expense	$ 181,000	$ 131,000	$ 470,000	$ 536,000
The Equity Incentive Plans [Member] \| Director [Member]
Share-Based Payment Arrangement, Expense	$ 59,000	$ 60,000	$ 175,000	$ 181,000