Fair value of equity interests and options issued or issuable to acquire the entity.

No definition available.

Name:	ibcp_BusinessAcquisitionEquityInterestAndOptionsIssuedFairValue
Namespace Prefix:	ibcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of shares of equity interest of acquirer issued to each holder of common stock of the acquiree in a business acquisition.

+ References

No definition available.

+ Details

Name:	ibcp_BusinessAcquisitionEquityInterestIssuedNumberOfShares
Namespace Prefix:	ibcp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Total amount of cash paid in lieu of fractional shares to each holder of common stock of the acquiree in a business acquisition.

+ References

No definition available.

+ Details

Name:	ibcp_BusinessCombinationConsiderationTransferredCashInLieuOfFractionalShares
Namespace Prefix:	ibcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460

+ Details

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ibcp_TCSBBancorpIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

RECENT ACQUISITION (Details) - USD ($) $ in Thousands		12 Months Ended
RECENT ACQUISITION (Details) - USD ($) $ in Thousands	Apr. 01, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Recent Acquisition [Abstract]
Fair value of equity issued under merger agreement		$ 0	$ 0	$ 64,536
Non-interest expense amount		0	0	3,465
TCSB Bancorp, Inc. [Member]
Recent Acquisition [Abstract]
Equity interest issued to each holder of common stock under merger agreement (in shares)	1.1166
Total value of common stock and cash paid in lieu of fractional shares	$ 5
Equity issued under merger agreement (in shares)	2,710,000
Options issued under merger agreement (in shares)	190,000
Fair value of equity issued under merger agreement	$ 64,500
Non-interest expense amount		$ 0	$ 0	$ 3,500