v3.25.4
First US Bancshares, Inc. (Parent Company Only) Financial Information - Statements of Operations (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2025
Sep. 30, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Sep. 30, 2024
Jun. 30, 2024
Mar. 31, 2024
Dec. 31, 2025
Dec. 31, 2024
Income:                    
Total income                 $ 1,140 $ 1,232
Expense                 5,536 4,754
Net income (loss) $ 2,129 $ 1,936 $ 155 $ 1,772 $ 1,714 $ 2,222 $ 2,127 $ 2,107 5,992 8,170
FUSB [Member]                    
Income:                    
Dividend income, First US Bank                 8,348 5,541
Total income                 8,348 5,541
Expense                 1,488 1,450
Gain before equity in undistributed income of subsidiaries                 6,860 4,091
Equity in undistributed income of subsidiaries                 (868) 4,079
Net income (loss)                 $ 5,992 $ 8,170