v3.26.1
Fair Value Measurements (Tables)
12 Months Ended
Dec. 31, 2025
NBT Bancorp Inc. 401(k) and Employee Stock Ownership Plan [Member]  
Fair Value Measurements [Abstract]  
Financial Instruments Recorded at Fair Value on a Recurring Basis
The following table presents the financial instruments recorded at fair value on a recurring basis by the Plan as of December 31, 2025 and 2024:
 
 
                             
Description
 
December 31, 2025
 
Level 1
 
Level 2
 
Level 3
Mutual funds
  $ 363,169,532    $ 363,169,532    $ -    $ -  
Common stock of NBT Bancorp Inc.
    30,074,182      30,074,182        -        -  
Stable value fund
    17,933,465      17,933,465        -        -  
Cash and money market funds
    31,988      31,988        -        -  
Total
  $ 411,209,167    $ 411,209,167    $ -    $ -  
 
                         
Description   December 31, 2024     Level 1     Level 2     Level 3  
Mutual funds
 $ 307,131,380   $ 307,131,380   $ -    $ -  
Common stock of NBT Bancorp Inc.
   35,226,305     35,226,305       -        -  
Stable value fund
   18,539,578     18,539,578       -        -  
Cash and money market funds
   86,728     86,728       -        -  
Total
 $ 360,983,991   $ 360,983,991   $ -    $ -