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Securities (Details) (USD $)	Mar. 31, 2015 Position	Dec. 31, 2014 Position
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,055,372,000us-gaap_AvailableForSaleSecuritiesAmortizedCost	$ 1,001,718,000us-gaap_AvailableForSaleSecuritiesAmortizedCost
Unrealized gains	17,158,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	14,823,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Unrealized losses	876,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	3,370,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Estimated fair value	1,071,654,000us-gaap_AvailableForSaleSecurities	1,013,171,000us-gaap_AvailableForSaleSecurities
Amortized costs of securities available for sale pledged to secure public deposits	1,400,000,000nbtb_AvailableForSaleSecuritiesPledgedAsCollateralForPublicDepositsAmortizedCost	1,400,000,000nbtb_AvailableForSaleSecuritiesPledgedAsCollateralForPublicDepositsAmortizedCost
Amortized costs of securities available for sale pledged as collateral for repurchase agreements	183,000,000nbtb_SecuritiesAvailableForSaleAmortizedCostPledgedAsCollateralForRepurchaseAgreementsAmortizedCost	208,800,000nbtb_SecuritiesAvailableForSaleAmortizedCostPledgedAsCollateralForRepurchaseAgreementsAmortizedCost
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	190,311,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	143,428,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
12 Months or Longer, Fair Value	52,886,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	244,836,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Total, Fair Value	243,197,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	388,264,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(424,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	(500,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
12 months or longer Unrealized Losses	(452,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	(2,870,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Total Unrealized Losses	(876,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	(3,370,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	46us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear	59us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
12 Months or Longer, Number of Positions	23us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear	58us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
Total, Number of Positions	69us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	117us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	456,773,000us-gaap_HeldToMaturitySecurities	454,361,000us-gaap_HeldToMaturitySecurities
Unrealized gains	5,796,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	2,721,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
Unrealized losses	1,345,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	2,088,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
Estimated fair value	461,224,000us-gaap_HeldToMaturitySecuritiesFairValue	454,994,000us-gaap_HeldToMaturitySecuritiesFairValue
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	20,513,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	69,566,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
12 Months or Longer, Fair Value	45,860,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	48,034,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Total, Fair Value	66,373,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	117,600,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(51,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	(165,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
12 Months or Longer, Unrealized Losses	(1,294,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	(1,923,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Total, Unrealized Losses	(1,345,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	(2,088,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
Unrealized Loss Position, Number of Positions [Abstract]
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	113nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear	112nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater Than or Equal to One Year	4nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear	10nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
Total, Number of Positions	117nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	122nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities. (in hundredths)	10.00%nbtb_ConcentrationOfRiskPercentageOfConsolidatedStockholdersEquityThreshold
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Within one year	19,250,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost
From one to five years	414,712,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost
From five to ten years	170,168,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost
After ten years	438,370,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost
Total, Amortized Cost	1,042,500,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Within one year	19,312,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
From one to five years	416,598,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
From five to ten years	173,750,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
After ten years	446,447,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue
Total, Fair Value	1,056,107,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Within one year	24,182,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount
From one to five years	16,047,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount
From five to ten years	90,418,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount
After ten years	326,126,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount
Amortized cost	456,773,000us-gaap_HeldToMaturitySecurities	454,361,000us-gaap_HeldToMaturitySecurities
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Within one year	24,260,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue
From one to five years	16,137,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
From five to ten years	91,502,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
After ten years	329,325,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue
Total, Fair Value	461,224,000us-gaap_HeldToMaturitySecuritiesFairValue	454,994,000us-gaap_HeldToMaturitySecuritiesFairValue
Mortgage-Backed [Member] | Government-sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	10,260,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	755,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Unrealized gains	25,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	113,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Unrealized losses	0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Estimated fair value	10,285,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	868,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	10,260,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	755,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	10,285,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	868,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Mortgage-Backed [Member] | U.S. Government Agency Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	727,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentDebtSecuritiesMember
Unrealized gains	122,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentDebtSecuritiesMember
Unrealized losses	0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentDebtSecuritiesMember
Estimated fair value	849,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentDebtSecuritiesMember
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	727,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentDebtSecuritiesMember
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	849,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_AssetBackedSecuritiesMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentDebtSecuritiesMember
State & Municipal [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	138,139,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	135,978,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized gains	1,370,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	674,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized losses	32,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	123,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Estimated fair value	139,477,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	136,529,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	7,482,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	43,514,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
12 Months or Longer, Fair Value	0us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	1,619,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Total, Fair Value	7,482,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	45,133,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(32,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	(116,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
12 Months or Longer, Unrealized Losses	0us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	(7,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Total, Unrealized Losses	(32,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	(123,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized Loss Position, Number of Positions [Abstract]
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	102nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	110nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater Than or Equal to One Year	0nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	6nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Total, Number of Positions	102nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	116nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	138,139,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	135,978,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	139,477,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	136,529,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	13,031,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	26,052,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
12 Months or Longer, Fair Value	45,860,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	46,415,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
Total, Fair Value	58,891,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	72,467,000us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(19,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	(49,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
12 Months or Longer, Unrealized Losses	(1,294,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	(1,916,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
Total, Unrealized Losses	(1,313,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	(1,965,000)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
Unrealized Loss Position, Number of Positions [Abstract]
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	11nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	2nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater Than or Equal to One Year	4nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	4nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
Total, Number of Positions	15nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember	6nbtb_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember
Collateralized Mortgage Obligations [Member] | Government-sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	307,647,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	317,628,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Unrealized gains	4,279,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	1,934,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Unrealized losses	1,313,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	1,965,000us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Estimated fair value	310,613,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	317,597,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	307,647,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	317,628,000us-gaap_HeldToMaturitySecurities / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	310,613,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	317,597,000us-gaap_HeldToMaturitySecuritiesFairValue / us-gaap_DebtSecurityAxis = us-gaap_CollateralizedMortgageObligationsMember / nbtb_HeldToMaturityDebtSecurityAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
US Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	13,019,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember	23,041,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember
Unrealized gains	37,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember	70,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember
Unrealized losses	0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember	0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember
Estimated fair value	13,056,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember	23,111,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember
Federal Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	402,255,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	332,193,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized gains	1,080,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	327,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized losses	584,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	2,606,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Estimated fair value	402,751,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	329,914,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	159,455,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	66,528,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
12 Months or Longer, Fair Value	39,721,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	198,151,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Total, Fair Value	199,176,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	264,679,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(331,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	(226,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
12 months or longer Unrealized Losses	(253,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	(2,380,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Total Unrealized Losses	(584,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	(2,606,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	13us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	8us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
12 Months or Longer, Number of Positions	4us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	16us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Total, Number of Positions	17us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	24us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
State & Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	37,807,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	37,035,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized gains	621,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	587,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized losses	5,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	52,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Estimated fair value	38,423,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	37,570,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	1,939,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	8,818,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
12 Months or Longer, Fair Value	0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	1,321,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Total, Fair Value	1,939,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	10,139,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(5,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	(42,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
12 months or longer Unrealized Losses	0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	(10,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Total Unrealized Losses	(5,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	(52,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	4us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	33us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
12 Months or Longer, Number of Positions	0us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	5us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Total, Number of Positions	4us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember	38us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	11,159,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	10,400,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
12 Months or Longer, Fair Value	4,759,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	35,565,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Total, Fair Value	15,918,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	45,965,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(20,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	(36,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
12 months or longer Unrealized Losses	(60,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	(254,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Total Unrealized Losses	(80,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	(290,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	16us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	10us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
12 Months or Longer, Number of Positions	14us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	31us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Total, Number of Positions	30us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	41us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Mortgage-backed Securities, Issued by US Government-Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	321,746,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember	339,190,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Unrealized gains	8,838,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember	7,597,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Unrealized losses	16,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember	224,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Estimated fair value	330,568,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember	346,563,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Mortgage-backed Securities, Issued by US Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	16,406,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember	17,367,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember
Unrealized gains	893,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember	863,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember
Unrealized losses	64,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember	66,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember
Estimated fair value	17,235,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember	18,164,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = nbtb_MortgageBackedSecuritiesIssuedByUSGovernmentSecuritiesMember
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	17,116,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	57,682,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
12 Months or Longer, Fair Value	5,169,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	6,598,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
Total, Fair Value	22,285,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	64,280,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(60,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	(196,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
12 months or longer Unrealized Losses	(23,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	(74,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
Total Unrealized Losses	(83,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	(270,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	12us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	8us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
12 Months or Longer, Number of Positions	3us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	4us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
Total, Number of Positions	15us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember	12us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedMortgageObligationsMember
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	213,999,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	199,837,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Unrealized gains	2,336,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	1,828,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Unrealized losses	54,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	234,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Estimated fair value	216,281,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember	201,431,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Collateralized Mortgage Obligations, U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	37,268,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember	40,237,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember
Unrealized gains	554,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember	497,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember
Unrealized losses	29,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember	36,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember
Estimated fair value	37,793,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember	40,698,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,872,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	12,818,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Unrealized gains	2,799,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	3,054,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Unrealized losses	124,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	152,000us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Estimated fair value	15,547,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	15,720,000us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	642,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
12 Months or Longer, Fair Value	3,237,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	3,201,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Total, Fair Value	3,879,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	3,201,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(8,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
12 months or longer Unrealized Losses	(116,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	(152,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Total Unrealized Losses	$ (124,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	$ (152,000)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	1us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	0us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
12 Months or Longer, Number of Positions	2us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	2us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Total, Number of Positions	3us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember	2us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1 / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember

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