SHARE BASED COMPENSATION AND BENEFIT PLANS, Options Exercised During the Periods (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Information regarding options exercised [Abstract]
Employee matching contribution, percentage	50.00%	50.00%	50.00%
Maximum contribution of employees' eligible wages	8.00%	8.00%	8.00%
Maximum matching contribution, percent	6.00%
Employee stock ownership plan (ESOP), contributions	2.00%	2.00%	2.00%
401(k) and employee stock ownership plans amount expensed	$ 3,200	$ 2,600	$ 2,300
Performance-based compensation expense	15,700	9,500	9,800
Health care and life insurance expense	4,800	5,700	5,200
Stock Options [Member]
Information regarding options exercised [Abstract]
Intrinsic value	293	897	2,333
Cash proceeds received	57	706	1,420
Tax benefit realized	$ 61	$ 188	$ 490

Maximum percentage of employee gross pay the employer may contribute to a defined contribution plan.

No definition available.

Name:	ibcp_DefinedContributionPlanMaximumAnnualContributionsEmployerPercent
Namespace Prefix:	ibcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Expenditures for employee health care and life insurance benefits as provided for compensation.

+ References

No definition available.

+ Details

Name:	ibcp_EmployeeCompensationBenefitHealthCareAndLifeInsuranceExpense
Namespace Prefix:	ibcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This item represents the percentage of contributions during the period made by the entity to the Employee Stock Ownership Plan (ESOP).

+ References

No definition available.

+ Details

Name:	ibcp_EmployeeStockOwnershipPlanESOPContributionsToESOP
Namespace Prefix:	ibcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the expense recognized during the period arising from compensation arrangements for performance programs with employees, directors and certain consultants qualifying for treatment as employees.

+ References

No definition available.

+ Details

Name:	ibcp_IncentiveBasedCompensationExpense
Namespace Prefix:	ibcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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

- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

+ Details

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

- Definition

Amount of tax benefit from exercise of option under share-based payment arrangement.

+ References

+ Details

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

- Definition

Amount of cash inflow from exercise of option under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=SL79508275-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: