XML 51 R39.htm IDEA: XBRL DOCUMENT
v3.19.2

Securities, Held to Maturity (Details) - USD ($) $ in Thousands | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | $ 744,601 | $ 783,599
Unrealized gains | 11,493 | 3,362
Unrealized losses | 1,099 | 8,286
Estimated fair value | 754,995 | 778,675
Amortized costs of securities available for sale and held to maturity pledged to secure public deposits | 1,400,000 | 1,500,000
Amortized costs of securities AFS and HTM pledged as collateral for repurchase agreements | 197,400 | 215,300
Federal Agency [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 19,996 | 19,995
Unrealized gains | 46 | 52
Unrealized losses | 0 | 0
Estimated fair value | 20,042 | 20,047
Mortgage-Backed, Government Sponsored Enterprises [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 163,049 | 164,618
Unrealized gains | 2,334 | 712
Unrealized losses | 484 | 2,773
Estimated fair value | 164,899 | 162,557
Mortgage-Backed, U.S. Government Agency Securities [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 14,530 | 15,230
Unrealized gains | 921 | 403
Unrealized losses | 0 | 0
Estimated fair value | 15,451 | 15,633
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 232,825 | 257,475
Unrealized gains | 2,712 | 1,097
Unrealized losses | 539 | 3,897
Estimated fair value | 234,998 | 254,675
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 103,457 | 83,148
Unrealized gains | 3,303 | 767
Unrealized losses | 0 | 0
Estimated fair value | 106,760 | 83,915
State & Municipal [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 210,744 | 243,133
Unrealized gains | 2,177 | 331
Unrealized losses | 76 | 1,616
Estimated fair value | $ 212,845 | $ 241,848

X
- Definition This represents the amortized costs of securities available for sale and held to maturity that are pledged as collateral for securities sold under repurchase agreements. + References No definition available. + Details
Name: | nbtb_AmortizedCostsOfSecuritiesAvailableForSaleAndHeldToMaturityPledgedAsCollateralForRepurchaseAgreements
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This represents the available for sale and held to maturity securities that are pledged as collateral to secure public deposits and for other purposes required or permitted by law. + References No definition available. + Details
Name: | nbtb_AmortizedCostsOfSecuritiesAvailableForSaleAndHeldToMaturityPledgedToSecurePublicDeposits
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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

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

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

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