Debt Instrument, interest rate, stated rate inclusive of interest rate swap which had expired as of end of year.

No definition available.

Name:	indb_DebtInstrumentinterestratestatedrateinclusiveofinterestrateswapexpired
Namespace Prefix:	indb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=indb_CapitalTrustVPreferredSecuritiesDueIn2037Member
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Data Type:	na
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- Details

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- Details

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- Details

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- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SubordinatedDebtMember
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- Details

Name:	us-gaap_DebtInstrumentAxis=indb_SubordinatedDebenturesDueinNovember2019MemberDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

BORROWINGS (Trust Preferred Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Face Amount	$ 74.0	$ 71.0
Junior Subordinated Debentures [Member] \| Capital Trust V Preferred Securities Due in 2037 [Member]
Debt Instrument [Line Items]
Face Amount	$ 50.0
Debt Instrument, interest rate, stated rate inclusive of interest rate swap - expired	2.84%
Fixed rate	4.27%
Junior Subordinated Debentures [Member] \| Capital Trust V Preferred Securities Due in 2037 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.48%
Junior Subordinated Debentures [Member] \| Slades Ferry Trust I Preferred Securities Due in 2034 [Member]
Debt Instrument [Line Items]
Face Amount	$ 10.0
Fixed rate	5.59%
Junior Subordinated Debentures [Member] \| Slades Ferry Trust I Preferred Securities Due in 2034 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.79%
Junior Subordinated Debentures [Member] \| Central Bancorp Capital Trust I Securities Due in 2034 [Member]
Debt Instrument [Line Items]
Face Amount	$ 5.1
Fixed rate	5.23%
Junior Subordinated Debentures [Member] \| Central Bancorp Capital Trust I Securities Due in 2034 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.44%
Junior Subordinated Debentures [Member] \| Central Bancorp Capital Trust II Securities Due in 2037 [Member]
Debt Instrument [Line Items]
Face Amount	$ 5.9
Junior Subordinated Debentures [Member] \| Central Bancorp Capital Trust II Securities Due in 2037 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.65%
Fixed rate	4.44%
Subordinated Debt [Member] \| Subordinated Debentures Due in November 2019 [Member] [Domain]
Debt Instrument [Line Items]
Fixed rate	4.75%
Subordinated Debt [Member] \| Subordinated Debentures Due in November 2019 [Member] [Domain] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.98%