DEPOSITS (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Summary of deposit [Abstract]
Noninterest-bearing demand	$ 848,798	$ 809,437
Interest bearing demand	614,316	642,918
Savings and money market accounts	822,493	742,685
Certificates of deposit	102,338	103,547
Total deposits	2,387,945	2,298,587
FDIC insurance limit on deposit accounts	250	250
Time deposits that exceed FDIC insurance limit	$ 29,900	$ 28,800

Amount of deposits in savings and money market accounts.

No definition available.

Name:	mcbc_DepositsSavingsAndMoneyMarketDeposits
Namespace Prefix:	mcbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the amount of the Federal Deposit Insurance Corporation (FDIC) insurance limit on deposit accounts.

+ References

No definition available.

+ Details

Name:	mcbc_FDICInsuranceLimitOnDepositAccounts
Namespace Prefix:	mcbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The aggregate amount of time deposits that exceed the Federal Deposit insurance Corporation insurance limits.

+ References

No definition available.

+ Details

Name:	mcbc_TimeDepositsExceedingFDICInsuranceLimits
Namespace Prefix:	mcbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of money in accounts that may bear interest and that the depositor is entitled to withdraw at any time without prior notice.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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

- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of interest-bearing domestic certificate of deposit liabilities.

+ References

+ Details

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

- Definition

The aggregate amount of all domestic and foreign noninterest-bearing deposits liabilities held by the entity.

+ References

+ Details

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