Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Revenue from Contract with Customer [Abstract]
Service Charges on Deposit Accounts	$ 4,431	$ 4,544
Merchant Discount Fees	3,405	3,121
ATM Fees	654	687
Wealth management and advisory services	5,582	5,137
Fees and Commissions Investment Management	560	477
Merchant Processing Income	431	293
Other noninterest income - ASC 606	$ 974	$ 822

Amounts charged for use of automated teller machines or remote service units.

No definition available.

Name:	indb_ATMFees
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fees and commissions earned on the sales of mutual fund shares, unit investment trust shares, general securities and life insurance products.

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No definition available.

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Name:	indb_FeesandCommissionsInvestmentManagement
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Commission and fee income earned by referring third party merchant processing partners to the Company's customers.

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No definition available.

+ Details

Name:	indb_MerchantProcessingIncome
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Other various types of noninterest income that falls within the scope of ASC 606. This category of other noninterest income includes but is not limited to safe deposit rent, 1031 exchange fee revenue and foreign currency.

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No definition available.

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Name:	indb_OthernoninterestincomeASC606
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Includes amounts charged depositors for: (1) maintenance of their accounts (maintenance charges); (2) failure to maintain specified minimum balances on account; (3) exceeding the number of checks or transactions allowed to be processed in a given period; (4) checks drawn on no minimum balance deposit accounts; (5) withdrawals from non transaction deposit accounts; (6) closing savings accounts before a specified minimum period of time has elapsed; (7) accounts which have remained inactive for extended periods of time or which have become dormant; (8) checks drawn against insufficient funds that the bank assesses regardless of whether it decides to pay, return or hold the check; (9) issuing stop payment orders; (10) certifying checks; and (11) accumulating or disbursing funds deposited in IRAs or Keogh Plan accounts when not handled by the bank's trust department. This item does not include penalties assessed on the early withdrawal of time deposits.

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No definition available.

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Name:	indb_ServiceChargesOnDepositAccounts
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Revenue earned from investment advisory services, including asset management fees.

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No definition available.

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Name:	indb_Wealthmanagementandadvisoryservices
Namespace Prefix:	indb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of earnings on fees charged to merchants for the cardholder's use of a credit card. Excludes interest income earned on credit card balances, transactions and credit card services including late, over limit, and annual fees.

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No definition available.

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Name:	us-gaap_MerchantDiscountFees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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