XML 61 R51.htm IDEA: XBRL DOCUMENT
v3.23.1

Allowance for Credit Losses and Credit Quality of Loans, Performance of Modified Loans (Details) - ASU 2022-02 [Member] $ in Thousands | Mar. 31, 2023 USD ($)
--- | ---
Current [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | $ 43
31-60 Days Past Due [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | 0
61-90 Days Past Due [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | 0
Greater Than 90 Days Past Due [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | 0
Residential [Member] | Current [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | 43
Residential [Member] | 31-60 Days Past Due [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | 0
Residential [Member] | 61-90 Days Past Due [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | 0
Residential [Member] | Greater Than 90 Days Past Due [Member] |
Performance of Modified Loans [Abstract] |
Amortized cost | $ 0

X
- Definition Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty. + References No definition available. + Details
Name: | nbtb_FinancingReceivableModifiedInPeriodAmount
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=nbtb_AccountingStandardsUpdate202202Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=nbtb_FinancingReceivables31To60DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=nbtb_FinancingReceivables61To90DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=nbtb_FinancingReceivablesGreaterThan90DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |