Fair Value Measurements (Details) - USD ($)	Sep. 30, 2016	Dec. 31, 2015
ASSETS
Trading Securities	$ 809,000	$ 356,000
Securities - available for sale	387,008,000	367,249,000
Loans held for sale	13,334,000	5,990,000
Derivative Asset, Fair Value, Gross Asset	41,905,000	23,072,000
Recurring fair value measurements
LIABILITIES
TOTAL RECURRING FAIR VALUE MEASUREMENTS	399,867,000	370,587,000
Recurring fair value measurements \| Trading Securities [Member]
ASSETS
Trading Securities	809,000	356,000
Recurring fair value measurements \| U.S. Government agency securities
ASSETS
Securities - available for sale	25,306,000	30,215,000
Recurring fair value measurements \| Agency mortgage-backed securities
ASSETS
Securities - available for sale	185,573,000	210,937,000
Recurring fair value measurements \| Agency collateralized mortgage obligations
ASSETS
Securities - available for sale	108,596,000	63,584,000
Recurring fair value measurements \| Municipal Bonds [Member]
ASSETS
Securities - available for sale	4,360,000	4,659,000
Recurring fair value measurements \| Single issuer trust preferred securities issued by banks and insurers
ASSETS
Securities - available for sale	2,297,000	2,792,000
Recurring fair value measurements \| Pooled trust preferred securities issued by banks and insurers
ASSETS
Securities - available for sale	1,538,000	1,572,000
Recurring fair value measurements \| Small Business Administration Pooled Securities [Member]
ASSETS
Securities - available for sale	39,880,000	40,449,000
Recurring fair value measurements \| Equity securities
ASSETS
Securities - available for sale	19,458,000	13,041,000
Recurring fair value measurements \| Loans held for sale
ASSETS
Loans held for sale	13,334,000	5,990,000
Recurring fair value measurements \| Derivative Financial Instruments, Assets [Member]
ASSETS
Derivative Asset, Fair Value, Gross Asset	42,556,000	23,305,000
Recurring fair value measurements \| Derivative instruments
LIABILITIES
Liabilities, Fair Value Disclosure, Recurring	43,840,000	26,313,000
Nonrecurring fair value measurements
LIABILITIES
TOTAL NONRECURRING FAIR VALUE MEASUREMENTS	4,854,000	6,757,000
Nonrecurring fair value measurements \| Collateral dependent impaired loans
ASSETS
Assets, Fair Value Disclosure, Nonrecurring	3,056,000	4,598,000
Nonrecurring fair value measurements \| Other real estate owned and other foreclosed assets
ASSETS
Assets, Fair Value Disclosure, Nonrecurring	1,798,000	2,159,000
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Recurring fair value measurements
LIABILITIES
TOTAL RECURRING FAIR VALUE MEASUREMENTS	20,267,000	13,397,000
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Recurring fair value measurements \| Trading Securities [Member]
ASSETS
Trading Securities	809,000	356,000
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Recurring fair value measurements \| Municipal Bonds [Member]
ASSETS
Securities - available for sale		0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Recurring fair value measurements \| Small Business Administration Pooled Securities [Member]
ASSETS
Securities - available for sale	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Recurring fair value measurements \| Equity securities
ASSETS
Securities - available for sale	19,458,000	13,041,000
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Nonrecurring fair value measurements
LIABILITIES
TOTAL NONRECURRING FAIR VALUE MEASUREMENTS	0	0
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements
LIABILITIES
TOTAL RECURRING FAIR VALUE MEASUREMENTS	378,062,000	355,618,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| U.S. Government agency securities
ASSETS
Securities - available for sale	25,306,000	30,215,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Agency mortgage-backed securities
ASSETS
Securities - available for sale	185,573,000	210,937,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Agency collateralized mortgage obligations
ASSETS
Securities - available for sale	108,596,000	63,584,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Municipal Bonds [Member]
ASSETS
Securities - available for sale	4,360,000	4,659,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Single issuer trust preferred securities issued by banks and insurers
ASSETS
Securities - available for sale	2,297,000	2,792,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Small Business Administration Pooled Securities [Member]
ASSETS
Securities - available for sale	39,880,000	40,449,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Loans held for sale
ASSETS
Securities - available for sale	13,334,000	5,990,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Derivative Financial Instruments, Assets [Member]
ASSETS
Derivative Asset, Fair Value, Gross Asset	42,556,000	23,305,000
Significant Other Observable Inputs (Level 2) \| Recurring fair value measurements \| Derivative instruments
LIABILITIES
Liabilities, Fair Value Disclosure, Recurring	43,840,000	26,313,000
Significant Other Observable Inputs (Level 2) \| Nonrecurring fair value measurements
LIABILITIES
TOTAL NONRECURRING FAIR VALUE MEASUREMENTS	0	0
Significant Unobservable Inputs (Level 3) \| Recurring fair value measurements
LIABILITIES
TOTAL RECURRING FAIR VALUE MEASUREMENTS	1,538,000	1,572,000
Significant Unobservable Inputs (Level 3) \| Recurring fair value measurements \| U.S. Government agency securities
ASSETS
Securities - available for sale
Significant Unobservable Inputs (Level 3) \| Recurring fair value measurements \| Municipal Bonds [Member]
ASSETS
Securities - available for sale		0
Significant Unobservable Inputs (Level 3) \| Recurring fair value measurements \| Pooled trust preferred securities issued by banks and insurers
ASSETS
Securities - available for sale	1,538,000	1,572,000
Significant Unobservable Inputs (Level 3) \| Recurring fair value measurements \| Small Business Administration Pooled Securities [Member]
ASSETS
Securities - available for sale	0	0
Significant Unobservable Inputs (Level 3) \| Nonrecurring fair value measurements
LIABILITIES
TOTAL NONRECURRING FAIR VALUE MEASUREMENTS	4,854,000	6,757,000
Significant Unobservable Inputs (Level 3) \| Nonrecurring fair value measurements \| Collateral dependent impaired loans
ASSETS
Assets, Fair Value Disclosure, Nonrecurring	3,056,000	4,598,000
Significant Unobservable Inputs (Level 3) \| Nonrecurring fair value measurements \| Other real estate owned and other foreclosed assets
ASSETS
Assets, Fair Value Disclosure, Nonrecurring	$ 1,798,000	$ 2,159,000

Assets and liabilities, fair value disclosure nonrecurring.

No definition available.

Name:	indb_AssetsAndLiabilitiesFairValueDisclosureNonrecurring
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Assets and liabilities, fair value disclosure recurring.

+ References

No definition available.

+ Details

Name:	indb_AssetsAndLiabilitiesFairValueDisclosureRecurring
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_AssetsFairValueDisclosureNonrecurring
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=SL51823488-111719

+ Details

Name:	us-gaap_DerivativeFairValueOfDerivativeAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Aggregation of the liabilities reported on the balance sheet measured at fair value on a recurring basis by the entity.

+ References

No definition available.

+ Details

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

- Definition

Amount, after allowance for bad debt, of mortgage loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

+ Details

Name:	us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroupMortgage
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

+ Details

Name:	us-gaap_TradingSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant