STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR PLAN BENEFITS - NBT Bancorp Inc. 401(k) and Employee Stock Ownership Plan [Member] - USD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
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| Net investment income: | ||
| Net appreciation in fair value of investments | $ 23,419,439 | $ 33,173,589 |
| Dividends | 20,873,491 | 12,838,626 |
| Interest | 568,966 | 528,817 |
| Total net investment income | 44,861,896 | 46,541,032 |
| Interest income on notes receivable from participants | 282,451 | 260,292 |
| Contributions: | ||
| Participants | 15,806,249 | 13,792,131 |
| Employer | 6,591,657 | 7,088,166 |
| Rollovers | 15,202,083 | 4,957,880 |
| Total contributions | 37,599,989 | 25,838,177 |
| Total additions | 82,744,336 | 72,639,501 |
| Deductions | ||
| Distributions to participants | (33,787,979) | (26,959,027) |
| Administrative expenses | (28,590) | (25,806) |
| Total deductions | (33,816,569) | (26,984,833) |
| Net increase in net assets available for plan benefits | 48,927,767 | 45,654,668 |
| Net assets available for plan benefits | ||
| Beginning of year | 366,442,879 | 320,788,211 |
| End of year | $ 415,370,646 | $ 366,442,879 |
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- Definition Amount of decrease in net asset available for benefit to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- References No definition available.
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- Definition Amount of decrease in net asset available for benefit from administrative expense incurred by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of decrease in net asset available for benefit from payment of benefit to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, withdrawal. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of increase in net asset available for benefit to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of increase (decrease) in net asset available for benefit to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of increase (decrease) in net asset available for benefit from realized and unrealized gain (loss) on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of increase (decrease) in net asset available for benefit from income (loss) on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, realized and unrealized gain (loss) on investment. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- References No definition available.
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- Definition Amount of increase in net asset available for benefit from contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- References No definition available.
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- Definition Amount of increase in net asset available for benefit from dividend income on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of increase in net asset available for benefit from cash contribution from employer of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of increase in net asset available for benefit from interest income on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Excludes interest income on note receivable from participant. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Amount of increase in net asset available for benefit from interest income on note receivable from participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, excluding rollover, of increase in net asset available for benefit from contribution by participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of increase in net asset available for benefit from contribution transferred from another qualified plan or from individual retirement account of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Excludes contribution for participant transmitted by employer of participant in EBP. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of asset less liability available to pay benefit of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, aggregation of participants' individual account balances. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References No definition available.
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- Details
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