v3.26.1
Stock Based Compensation - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Dec. 02, 2024
Nov. 18, 2024
Nov. 18, 2023
Jun. 01, 2023
May 25, 2023
Nov. 18, 2021
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Number of shares committed to be released each year, ESOP             7,678   7,678   15,354
Unearned compensation for ESOP             $ 4,084,000   $ 4,084,000   $ 4,357,000
Share price       $ 7.99              
Income tax benefit             227,000 $ (12,000) $ (46,000) $ 17,000  
Restricted stock awards granted       2,478              
Fair value related to grant $ 1,000,000     $ 20,000              
Restricted Stock Awards [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Restricted stock awards time-vest   50.00% 50.00%                
Minimum [Member] | Restricted Stock Awards [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Issued stock option granted, term                 3 years    
Directors and Members [Member] | Restricted Stock Awards [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Stock issued during period, shares, restricted stock award           98,850          
Share price                 $ 11.95    
Total fair value related to stock options granted                 $ 1,200,000    
2021 Equity Incentive Plan [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Common stock shares issued during period, new issues                 348,801    
Issued stock option granted, term                 10 years    
Stock options granted, outstanding         249,144            
2021 Equity Incentive Plan [Member] | Maximum [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Share-based payment arrangement, exercise of option                 249,144    
Stock issued during period, shares, restricted stock award                 99,657    
2021 Equity Incentive Plan [Member] | Director [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Unearned compensation for ESOP             0   $ 0   96,000
Share based expense recognized             35,000 60,000 96,000 115,000  
Income tax benefit             9,000 17,000 26,000 33,000  
2024 Equity Incentive Plan [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Stock options unrecognized compensation expense             528,000   528,000   694,000
Stock awards unrecognized compensation expense             501,000   $ 501,000   $ 666,000
Common stock shares issued during period, new issues                 392,700    
Stock options granted, outstanding 280,500                    
Share based expense recognized             87,000 87,000 $ 165,000 174,000  
Income tax benefit             24,000 24,000 $ 44,000 48,000  
Weighted average future recognition period                 1 year 4 months 24 days   1 year 10 months 24 days
Restricted stock awards granted 112,200                    
2024 Equity Incentive Plan [Member] | Maximum [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Share-based payment arrangement, exercise of option                 280,500    
Stock issued during period, shares, restricted stock award                 112,200    
2024 Equity Incentive Plan [Member] | Director [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Share price $ 9.29                    
Share based expense recognized             75,000 91,000 $ 166,000 181,000  
Income tax benefit             $ 20,000 25,000 $ 45,000 50,000  
First Seacoast Bank Employee Stock Ownership Plan [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Number of shares committed to be released each year, ESOP             15,354   15,354    
Employee stock option compensation recognized             $ 49,000 $ 43,000 $ 107,000 $ 84,000  
Unearned compensation for ESOP             3,600,000   3,600,000   $ 3,700,000
Employee stock option unallocated share fair value             5,600,000   $ 5,600,000   4,500,000
Employee stock option plan [Member]                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Stock repurchase                 423,715    
Percentage of purchase price common stock                 100.00%    
Remaining principal balance of debt             $ 4,100,000   $ 4,100,000   $ 4,100,000