XML 21 R92.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018
Commitments and Contingent Liabilities [Abstract] |  |
Percentage of the Company's loans secured by real estate | 60.00% |
Federal Reserve Bank Requirement [Abstract] |  |
Federal Reserve Bank maintenance period | 14 days |
Average reserve at Federal Reserve Bank for maintenance period | $ 37,300 |
Maximum [Member] |  |
Guarantor Obligations [Abstract] |  |
Obligation instrument term | 1 year |
Unused lines of Credit [Member] |  |
Guarantor Obligations [Abstract] |  |
Commitments - maximum potential obligation | $ 340,703 | $ 313,987
Commitment to Extend Credits, Primarily Variable Rate [Member] |  |
Guarantor Obligations [Abstract] |  |
Commitments - maximum potential obligation | 1,579,414 | 1,420,795
Standby Letters of Credit [Member] |  |
Guarantor Obligations [Abstract] |  |
Commitments - maximum potential obligation | 34,479 | 41,194
Loans Sold with Recourse [Member] |  |
Guarantor Obligations [Abstract] |  |
Commitments - maximum potential obligation | $ 25,639 | $ 27,223

X
- Definition For banks and other depository institutions, the calculated average reserve balance outstanding for the specific period as of the Balance Sheet date. Includes noninterest bearing balances with the Federal Reserve Banks. + References No definition available. + Details
Name: | nbtb_AverageReserveBalancesWithFederalReserveBank
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Describe the approximate period of the guarantee or each group of similar guarantees, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | nbtb_GuarantorObligationsPeriod
Namespace Prefix: | nbtb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Specific period of time established required to maintain reserve balances with the Federal Reserve Bank, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | nbtb_MaintenancePeriodBasisFederalReserveBank
Namespace Prefix: | nbtb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The percentage of the Company's loans secured by real estate. + References No definition available. + Details
Name: | nbtb_PercentageOfCompanysLoansSecuredByRealEstate
Namespace Prefix: | nbtb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12069-110248 + Details
Name: | us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_UnusedLinesOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_CommitmentsToExtendCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_FinancialStandbyLetterOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=nbtb_LoansSoldWithRecourseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |