XML 77 R60.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Originated Loans [Member] | Commercial Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | $ 1,741,936 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember | $ 1,652,553 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,648,664 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 1,547,669 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 23,680 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 40,037 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 69,584 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 64,835 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 8 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 12 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 615,147 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember | 616,423 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 570,884 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 576,079 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 6,022 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 16,836 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 38,241 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 23,508 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,068,868 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember | 934,316 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,023,856 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 878,411 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 17,341 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 22,777 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 27,671 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 33,128 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 32,947 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember | 65,162 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 30,481 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 60,043 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 275 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 381 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,183 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 4,726 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 8 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 12 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 24,974 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember | 36,652 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 23,443 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 33,136 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 42 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 43 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,489 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 3,473 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalRealEstateFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Originated Loans [Member] | Business Banking Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 398,435 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember | 337,679 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 379,445 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember | 319,578 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 18,990 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember | 18,101 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 398,435 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember | 337,679 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 379,445 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember | 319,578 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 18,990 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember | 18,101 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember
Originated Loans [Member] | Consumer Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,858,724 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember | 1,752,950 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,847,216 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember | 1,742,728 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 11,508 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember | 10,222 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,310,050 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember | 1,161,844 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,306,095 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember | 1,158,800 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,955 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember | 3,044 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 492,880 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember | 532,823 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 485,463 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember | 525,777 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 7,417 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember | 7,046 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 55,794 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember | 58,283 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 55,658 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember | 58,151 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 136 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember | 132 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 848,842 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember | 733,221 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 838,816 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember | 725,308 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 10,026 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember | 7,913 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] | Residential Mortgage [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 848,842 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember | 733,221 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] | Residential Mortgage [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 838,816 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember | 725,308 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] | Residential Mortgage [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 10,026 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember | 7,913 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 275,152 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember | 332,240 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 249,666 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 290,702 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 5,486 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 8,413 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 20,000 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 33,125 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 75,264 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember | 103,226 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 63,630 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 85,692 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,840 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 2,230 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 8,794 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 15,304 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_CommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 199,888 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember | 229,014 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 186,036 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 205,010 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,646 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 6,183 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 11,206 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 17,821 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_AgriculturalFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Acquired Loans [Member] | Business Banking Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 58,179 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember | 70,149 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 53,264 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember | 65,437 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 4,915 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember | 4,712 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 58,179 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember | 70,149 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 53,264 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember | 65,437 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_NonClassifiedMember
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 4,915 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember | 4,712 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nbtb_BusinessBankingCreditExposureMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_SmallBusinessFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = nbtb_ClassifiedMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 147,256 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember | 219,587 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 146,494 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember | 218,795 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 762 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember | 792 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 65,223 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember | 125,086 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 65,063 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember | 124,922 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 160 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember | 164 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_IndirectFinancingReceivableMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 76,716 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember | 87,076 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 76,154 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember | 86,506 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 562 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember | 570 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_HomeEquityFinancingReceivablesMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 5,317 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember | 7,425 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 5,277 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember | 7,367 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 40 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember | 58 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nbtb_DirectFinancingReceivableMemberMember
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 266,747 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember | 308,416 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 262,883 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember | 304,544 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,864 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember | 3,872 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] | Residential Mortgage [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 266,747 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember | 308,416 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] | Residential Mortgage [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 262,883 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember | 304,544 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_PerformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] | Residential Mortgage [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | $ 3,864 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember | $ 3,872 us-gaap_NotesReceivableNet / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ResidentialPortfolioSegmentMember / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / nbtb_FinancingReceivableInformationByPaymentActivityAxis = us-gaap_NonperformingFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember

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- Definition Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 3 -Article 5 + Details
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