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SECURITIES (Details 1) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Available-for-sale Securities:    
Amortized Cost $ 343,093us-gaap_AvailableForSaleSecuritiesAmortizedCost $ 360,317us-gaap_AvailableForSaleSecuritiesAmortizedCost
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax 8,832us-gaap_AvailableForSaleEquitySecuritiesAccumulatedGrossUnrealizedGainBeforeTax 7,675us-gaap_AvailableForSaleEquitySecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax (3,371)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax (11,130)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Fair Value 348,554us-gaap_AvailableForSaleSecurities 356,862us-gaap_AvailableForSaleSecurities
Held-to-maturity Securities:    
Amortized Cost 375,453us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment 350,652us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain 7,747us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain 3,012us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss (3,501)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss (7,209)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
Fair Value 379,699us-gaap_HeldToMaturitySecuritiesFairValue 346,455us-gaap_HeldToMaturitySecuritiesFairValue
Available-for-sale Securities and Held-to-maturity Securities:    
Amortized Cost 718,546indb_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesAmortizedCost 710,969indb_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesAmortizedCost
Gross Unrealized Gains 16,579indb_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesGrossUnrealizedGains 10,687indb_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesGrossUnrealizedGains
Gross Unrealized Losses 6,872indb_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesGrossUnrealizedLosses 18,339indb_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesGrossUnrealizedLosses
Fair Value 728,253us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities 703,317us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities
U.S. Government agency securities    
Available-for-sale Securities:    
Amortized Cost 41,369us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
41,331us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax 139us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
3us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax (22)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(885)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair Value 41,486us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
40,449us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
U.S. treasury securities [Member]    
Held-to-maturity Securities:    
Amortized Cost 1,010us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
1,011us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain 63us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
31us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
Fair Value 1,073us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
1,042us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USTreasurySecuritiesMember
Agency mortgage-backed securities [Member]    
Available-for-sale Securities:    
Amortized Cost 211,168us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
232,742us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax 7,203us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
6,405us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax (693)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
(4,556)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fair Value 217,678us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
234,591us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Held-to-maturity Securities:    
Amortized Cost 159,522us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
155,067us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain 5,422us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
1,917us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
(1,033)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fair Value 164,944us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
155,951us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Agency collateralized mortgage obligations [Member]    
Available-for-sale Securities:    
Amortized Cost 63,059us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
58,765us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax 599us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
490us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax (623)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
(1,102)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Fair Value 63,035us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
58,153us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Held-to-maturity Securities:    
Amortized Cost 207,995us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
187,388us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain 2,141us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
824us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss (3,478)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
(6,176)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Fair Value 206,658us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
182,036us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
State, county, and municipal securities [Member]    
Available-for-sale Securities:    
Amortized Cost 5,106us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
5,439us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax 117us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
1us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax 0us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(28)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value 5,223us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
5,412us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities:    
Amortized Cost 424us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
678us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain 4us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
7us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value 428us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
685us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Single issuer trust preferred securities issued by banks [Member]    
Available-for-sale Securities:    
Amortized Cost 2,913us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
2,960us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax 12us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
14us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax (16)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
(22)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Fair Value 2,909us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
2,952us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Held-to-maturity Securities:    
Amortized Cost 1,500us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
1,503us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
23us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss (23)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Fair Value 1,477us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
1,526us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Pooled trust preferred securities issued by banks and insurers    
Available-for-sale Securities:    
Amortized Cost 7,906us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
8,083us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax 195us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
0us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax (1,780)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
(4,242)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
Fair Value 6,321us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
3,841us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= indb_PooledTrustPreferredSecuritiesIssuedByBanksAndInsurersMember
Marketable securities [Member]    
Available-for-sale Securities:    
Amortized Cost 11,572us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
10,997us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax 567us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
762us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax (237)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
(295)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
Fair Value 11,902us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
11,464us-gaap_AvailableForSaleSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_EquitySecuritiesMember
Corporate debt securities [Member]    
Held-to-maturity Securities:    
Amortized Cost 5,002us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember
5,005us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain 117us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember
210us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember
0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value $ 5,119us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember
$ 5,215us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CorporateDebtSecuritiesMember