XML 26 R32.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses (Details) (USD $) | 3 Months Ended |
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Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |
Balance as of Beginning of Period | $ 66,359,000 us-gaap_FinancingReceivableAllowanceForCreditLosses | $ 69,434,000 us-gaap_FinancingReceivableAllowanceForCreditLosses |
Charge-offs | (5,680,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs | (4,830,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs |
Recoveries | 1,038,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery | 1,234,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery |
Provision | 3,642,000 us-gaap_ProvisionForLoanLeaseAndOtherLosses | 3,596,000 us-gaap_ProvisionForLoanLeaseAndOtherLosses |
Balance as of Ending of Period | 65,359,000 us-gaap_FinancingReceivableAllowanceForCreditLosses | 69,434,000 us-gaap_FinancingReceivableAllowanceForCreditLosses |
Allowance for loan losses for acquired loan portfolio | 1.9 us-gaap_AllowanceForLoanAndLeaseLossesLoansAcquired | 0 us-gaap_AllowanceForLoanAndLeaseLossesLoansAcquired |
Provision expense and net charge-offs related to acquired loans | 600,000 nbtb_AllowanceForLoanAndLeaseLossesLoansAcquiredProvisionAndChargeOffs | 200,000 nbtb_AllowanceForLoanAndLeaseLossesLoansAcquiredProvisionAndChargeOffs |
Allowance loan losses [Abstract] |  |  |
Allowance for loan losses | 65,359,000 us-gaap_FinancingReceivableAllowanceForCreditLosses | 69,434,000 us-gaap_FinancingReceivableAllowanceForCreditLosses |
Allowance for loans individually evaluated for impairment | 2,950,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 |  | 1,100,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Allowance for loans collectively evaluated for impairment | 62,409,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment |  | 65,259,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Ending balance of loans | 5,623,023,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |  | 5,595,271,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Commercial Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |
Balance as of Beginning of Period | 32,433,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember | 35,090,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |
Charge-offs | (798,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember | (479,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |
Recoveries | 234,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember | 399,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |
Provision | (591,000)us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember | (573,000)us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |
Balance as of Ending of Period | 31,278,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember | 34,437,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |
Allowance loan losses [Abstract] |  |  |
Allowance for loan losses | 31,278,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember | 34,437,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |
Allowance for loans individually evaluated for impairment | 2,950,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 1,100,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Allowance for loans collectively evaluated for impairment | 28,328,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 31,333,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Ending balance of loans | 2,484,300,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 2,473,702,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Consumer Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |
Balance as of Beginning of Period | 26,720,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 27,694,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Charge-offs | (4,378,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | (4,032,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Recoveries | 748,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 741,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Provision | 3,066,000 us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 4,033,000 us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Balance as of Ending of Period | 26,156,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 28,436,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Allowance loan losses [Abstract] |  |  |
Allowance for loan losses | 26,156,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 28,436,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Allowance for loans individually evaluated for impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Allowance for loans collectively evaluated for impairment | 26,156,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 26,720,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance of loans | 2,013,123,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 2,005,980,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Residential Real Estate Mortgages [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |
Balance as of Beginning of Period | 7,130,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | 6,520,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
Charge-offs | (504,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | (319,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
Recoveries | 56,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | 94,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
Provision | 1,016,000 us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | (70,000)us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
Balance as of Ending of Period | 7,698,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | 6,225,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
Allowance loan losses [Abstract] |  |  |
Allowance for loan losses | 7,698,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | 6,225,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |
Allowance for loans individually evaluated for impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Allowance for loans collectively evaluated for impairment | 7,698,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 7,130,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Ending balance of loans | 1,125,600,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 1,115,589,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Unallocated [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |
Balance as of Beginning of Period | 76,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 130,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Charge-offs | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Recoveries | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Provision | 151,000 us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 206,000 us-gaap_ProvisionForLoanLeaseAndOtherLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Balance as of Ending of Period | 227,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 336,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance loan losses [Abstract] |  |  |
Allowance for loan losses | 227,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 336,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loans collectively evaluated for impairment | 227,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  | 76,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Originated Loans [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 4,904,253,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember |  | 4,847,937,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember
Ending balance of loans individually evaluated for impairment | 22,945,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember |  | 20,121,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember
Ending balance of loans collectively evaluated for impairment | 4,881,308,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember |  | 4,827,816,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember
Originated Loans [Member] | Commercial Loans [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 2,159,062,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 2,140,371,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Ending balance of loans individually evaluated for impairment | 12,253,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 11,079,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Ending balance of loans collectively evaluated for impairment | 2,146,809,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 2,129,292,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Originated Loans [Member] | Consumer Loans [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 1,880,448,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 1,858,724,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance of loans individually evaluated for impairment | 6,423,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 5,498,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance of loans collectively evaluated for impairment | 1,874,025,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 1,853,226,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Originated Loans [Member] | Residential Real Estate Mortgages [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 864,743,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 848,842,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Ending balance of loans individually evaluated for impairment | 4,269,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 3,544,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Ending balance of loans collectively evaluated for impairment | 860,474,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 845,298,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_OriginatedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Acquired Loans [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 718,770,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember |  | 747,334,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember
Ending balance of loans individually evaluated for impairment | 9,772,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember |  | 5,675,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember
Ending balance of loans collectively evaluated for impairment | 708,998,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember |  | 741,659,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember
Acquired Loans [Member] | Commercial Loans [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 325,238,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 333,331,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Ending balance of loans individually evaluated for impairment | 9,772,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 5,675,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Ending balance of loans collectively evaluated for impairment | 315,466,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |  | 327,656,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Acquired Loans [Member] | Consumer Loans [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 132,675,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 147,256,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance of loans individually evaluated for impairment | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance of loans collectively evaluated for impairment | 132,675,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  | 147,256,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Acquired Loans [Member] | Residential Real Estate Mortgages [Member] |  |  |
Allowance loan losses [Abstract] |  |  |
Ending balance of loans | 260,857,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 266,747,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Ending balance of loans individually evaluated for impairment | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Ending balance of loans collectively evaluated for impairment | $ 260,857,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember |  | $ 266,747,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / nbtb_ClassOfFinancingReceivablesAxis = nbtb_AcquiredLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember

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- Definition Reduction to the allowance for credit losses related to acquired financing receivables deemed uncollectible and the sum of the periodic provision charged to earnings, based on an assessment of uncollectibility from the counterparty on account of acquired loan, lease or other credit losses, to reduce these accounts to the amount that approximates their net realizable value. + References No definition available. + Details
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- Definition Amount of addition to allowance reserve for credit loss arising from purchase of loan and lease portfolios. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph d -Article 9 + Details
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- Definition A valuation allowance for financing receivables that are expected to be uncollectible. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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- Definition Amount of recovery of financing receivables doubtful of collection that were previously charged off. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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- Definition Amount of direct write-downs of financing receivables charged against the allowance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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- Definition The balance of financing receivables that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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- Definition The balance of financing receivables that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5074-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 + Details
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- Definition Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 11 -Article 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.11) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
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