v3.26.1
FAIR VALUE MEASUREMENTS (Details) - Needham Bank 401(k) Plan - USD ($)
Dec. 31, 2025
Dec. 31, 2024
FAIR VALUE MEASUREMENTS    
Total investments at fair value $ 65,862,176 $ 55,770,982
Mutual funds    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 12,225,708 9,910,111
Collective investment trusts    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 33,875,824 27,984,130
Pooled separate accounts    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 7,300,690 6,008,358
Self-directed brokerage accounts    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 567,911 432,770
Common stock    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 11,892,043 11,435,613
Level 1    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 24,685,662 21,778,494
Level 1 | Mutual funds    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 12,225,708 9,910,111
Level 1 | Self-directed brokerage accounts    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 567,911 432,770
Level 1 | Common stock    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 11,892,043 11,435,613
Level 2    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 41,176,514 33,992,488
Level 2 | Collective investment trusts    
FAIR VALUE MEASUREMENTS    
Total investments at fair value 33,875,824 27,984,130
Level 2 | Pooled separate accounts    
FAIR VALUE MEASUREMENTS    
Total investments at fair value $ 7,300,690 $ 6,008,358