XML 50 R38.htm IDEA: XBRL DOCUMENT
v3.19.2

Securities, Available for Sale (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018
Debt securities, available-for-sale [Abstract] |  |  |  |  |
Amortized cost | $ 974,300 |  | $ 974,300 |  | $ 1,017,626
Unrealized gains | 7,551 |  | 7,551 |  | 1,216
Unrealized losses | 2,155 |  | 2,155 |  | 20,346
Estimated fair value | 979,696 |  | 979,696 |  | 998,496
Sales transactions of securities available for sale [Abstract] |  |  |  |  |
Gross realized gains | 0 | $ 0 | 53 | $ 0 |
Gross realized (losses) | 0 | 0 | (152) | 0 |
Net AFS realized (losses) | 0 | 0 | (99) | 0 |
Gains from calls on securities available for sale | 0 | 0 | 4 | 0 |
OTTI loss realized on equity investment | 0 | $ 0 | 0 | $ 0 |
Federal Agency [Member] |  |  |  |  |
Debt securities, available-for-sale [Abstract] |  |  |  |  |
Amortized cost | 52,987 |  | 52,987 |  | 84,982
Unrealized gains | 28 |  | 28 |  | 10
Unrealized losses | 178 |  | 178 |  | 693
Estimated fair value | 52,837 |  | 52,837 |  | 84,299
State & Municipal [Member] |  |  |  |  |
Debt securities, available-for-sale [Abstract] |  |  |  |  |
Amortized cost | 9 |  | 9 |  | 30,136
Unrealized gains | 0 |  | 0 |  | 16
Unrealized losses | 0 |  | 0 |  | 237
Estimated fair value | 9 |  | 9 |  | 29,915
Mortgage-Backed, Government Sponsored Enterprises [Member] |  |  |  |  |
Debt securities, available-for-sale [Abstract] |  |  |  |  |
Amortized cost | 458,878 |  | 458,878 |  | 493,225
Unrealized gains | 3,624 |  | 3,624 |  | 439
Unrealized losses | 666 |  | 666 |  | 10,354
Estimated fair value | 461,836 |  | 461,836 |  | 483,310
Mortgage-Backed, U.S. Government Agency Securities [Member] |  |  |  |  |
Debt securities, available-for-sale [Abstract] |  |  |  |  |
Amortized cost | 36,447 |  | 36,447 |  | 29,190
Unrealized gains | 955 |  | 955 |  | 270
Unrealized losses | 11 |  | 11 |  | 475
Estimated fair value | 37,391 |  | 37,391 |  | 28,985
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member] |  |  |  |  |
Debt securities, available-for-sale [Abstract] |  |  |  |  |
Amortized cost | 351,250 |  | 351,250 |  | 332,409
Unrealized gains | 2,210 |  | 2,210 |  | 344
Unrealized losses | 847 |  | 847 |  | 7,211
Estimated fair value | 352,613 |  | 352,613 |  | 325,542
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member] |  |  |  |  |
Debt securities, available-for-sale [Abstract] |  |  |  |  |
Amortized cost | 74,729 |  | 74,729 |  | 47,684
Unrealized gains | 734 |  | 734 |  | 137
Unrealized losses | 453 |  | 453 |  | 1,376
Estimated fair value | $ 75,010 |  | $ 75,010 |  | $ 46,445

X
- Definition Gains from calls (requests of early payments) on trading securities which are classified as available-for-sale securities. + References No definition available. + Details
Name: | nbtb_GainsFromCallsOnSecuritiesAvailableForSale
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 Reference 2: 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 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting. + References No definition available. + Details
Name: | us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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_USStatesAndPoliticalSubdivisionsMember
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: |