XML 66 R55.htm IDEA: XBRL DOCUMENT
v3.25.2

Securities, HTM Securities in Continuous Unrealized Loss Position (Details) $ in Thousands | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2025 USD ($) Position | Dec. 31, 2024 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 21,843 | $ 16,605
12 months or longer | 612,678 | 640,538
Total | 634,521 | 657,143
Unrealized Loss Position, Unrealized Losses [Abstract] |  |
Less than 12 months | (175) | (114)
12 months or longer | (74,193) | (92,904)
Total | $ (74,368) | $ (93,018)
Unrealized Loss Position, Number of Positions [Abstract] |  |
Less than 12 months | Position | 13 | 13
12 months or longer | Position | 257 | 276
Total | Position | 270 | 289
HTM Securities [Abstract] |  |
HTM debt securities, nonaccrual | $ 0 | $ 0
Accrued interest reversed against interest income | 0 | 0
Collateral-dependent HTM debt securities | 0 | 0
Allowance for credit losses on HTM securities | 0 | 0
AIR on HTM debt securities | $ 4,400 | $ 4,400
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration] | Other Assets | Other Assets
Past Due [Member] |  |
HTM Securities [Abstract] |  |
HTM debt securities | $ 0 | $ 0
Federal Agency [Member] |  |
Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | 0 | 0
12 months or longer | 87,171 | 83,344
Total | 87,171 | 83,344
Unrealized Loss Position, Unrealized Losses [Abstract] |  |
Less than 12 months | 0 | 0
12 months or longer | (12,829) | (16,656)
Total | $ (12,829) | $ (16,656)
Unrealized Loss Position, Number of Positions [Abstract] |  |
Less than 12 months | Position | 0 | 0
12 months or longer | Position | 4 | 4
Total | Position | 4 | 4
Mortgage-Backed [Member] |  |
Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 11,031 | $ 0
12 months or longer | 174,596 | 189,271
Total | 185,627 | 189,271
Unrealized Loss Position, Unrealized Losses [Abstract] |  |
Less than 12 months | (4) | 0
12 months or longer | (27,390) | (34,865)
Total | $ (27,394) | $ (34,865)
Unrealized Loss Position, Number of Positions [Abstract] |  |
Less than 12 months | Position | 1 | 0
12 months or longer | Position | 33 | 34
Total | Position | 34 | 34
Collateralized Mortgage Obligations [Member] |  |
Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 0 | $ 7,147
12 months or longer | 193,085 | 198,978
Total | 193,085 | 206,125
Unrealized Loss Position, Unrealized Losses [Abstract] |  |
Less than 12 months | 0 | (7)
12 months or longer | (18,274) | (22,792)
Total | $ (18,274) | $ (22,799)
Unrealized Loss Position, Number of Positions [Abstract] |  |
Less than 12 months | Position | 0 | 1
12 months or longer | Position | 49 | 52
Total | Position | 49 | 53
State & Municipal [Member] |  |
Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 10,812 | $ 9,458
12 months or longer | 157,826 | 168,945
Total | 168,638 | 178,403
Unrealized Loss Position, Unrealized Losses [Abstract] |  |
Less than 12 months | (171) | (107)
12 months or longer | (15,700) | (18,591)
Total | $ (15,871) | $ (18,698)
Unrealized Loss Position, Number of Positions [Abstract] |  |
Less than 12 months | Position | 12 | 12
12 months or longer | Position | 171 | 186
Total | Position | 183 | 198
US Government Agencies Debt Securities and US Government-sponsored Enterprises Debt Securities [Member] |  |
HTM Securities [Abstract] |  |
Held-to-maturity debt securities, percentage | 66.00% | 66.00%
Local Municipal Bonds [Member] |  |
HTM Securities [Abstract] |  |
HTM debt securities | $ 89,100 | $ 84,700

X
- Definition Amount of reversed for accrued interest receivable on the HTM debt securities during the period. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityAccruedInterestReceivablesReversed
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of held-to-maturity securities that are collateral dependent. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityCollateralDependent
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityContinuousUnrealizedLossPositionQualitativeDisclosureAbstract
Namespace Prefix: | nbtb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss positions for 12 months or longer. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityContinuousUnrealizedLossPositions12MonthsOrLongerAccumulatedLoss
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss positions for 12 months or longer. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityContinuousUnrealizedLossPositions12MonthsOrLongerFairValue
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityContinuousUnrealizedLossPositionsAccumulatedLoss
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityContinuousUnrealizedLossPositionsFairValue
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss positions for less than 12 months. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityContinuousUnrealizedLossPositionsLessThan12MonthsAccumulatedLoss
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss positions for less than 12 months. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityContinuousUnrealizedLossPositionsLessThan12MonthsFairValue
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Disclosure regarding factors used to determine that the impairment of securities categorized as held-to-maturity where cost exceeds fair value is not an other than temporary impairment (OTTI). This item contains disclosure of the number of investment positions in the held-to-maturity investments determined to be temporarily impaired. + References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions
Namespace Prefix: | nbtb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityUnrealizedLossPositionsAccumulatedLossAbstract
Namespace Prefix: | nbtb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | nbtb_DebtSecuritiesHeldToMaturityUnrealizedLossPositionsFairValueAbstract
Namespace Prefix: | nbtb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of investment positions in held-to-maturity investments in a continuous unrealized loss position for greater than or equal to a year for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. + References No definition available. + Details
Name: | nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
Namespace Prefix: | nbtb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of investment positions in held-to-maturity investments in a continuous unrealized loss position for less than one year or normal operating cycle, if longer, for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. + References No definition available. + Details
Name: | nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
Namespace Prefix: | nbtb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of investment in debt security measured at amortized cost (held-to-maturity). + References No definition available. + Details
Name: | nbtb_PercentageOfHeldToMaturitySecurities
Namespace Prefix: | nbtb_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount, after allowance for credit loss, of accrued interest on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5C -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-5C Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-5 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-3A + Details
Name: | us-gaap_DebtSecuritiesHeldToMaturityAccruedInterestAfterAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Indicates line item in statement of financial position that includes accrued interest, after allowance for credit loss, on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-3A + Details
Name: | us-gaap_DebtSecuritiesHeldToMaturityAccruedInterestAfterAllowanceForCreditLossStatementOfFinancialPositionExtensibleList
Namespace Prefix: | us-gaap_
Data Type: | enum2:enumerationSetItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (aaa) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-5 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 + Details
Name: | us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at amortized cost (held-to-maturity) on nonaccrual status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_DebtSecuritiesHeldToMaturityNonaccrual
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-5 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-14 + Details
Name: | us-gaap_HeldToMaturitySecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedMortgageObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=nbtb_USGovernmentAgenciesDebtSecuritiesAndUSGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |