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Note 5 - Deposits (Details Textual) - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2022 | Dec. 31, 2021
Deposits, Total | $ 3,976,251,000 | $ 4,083,193,000
Increase (Decrease) in Deposits, Total | $ (107,000,000) |
Aggregate Increase (Decrease) in Percentage of Deposits | (2.60%) |
Time Deposits, at or Above FDIC Insurance Limit | $ 181,000,000 | $ 207,000,000

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- Definition The percentage of increase or (decrease) during the period in deposit liabilities. + References No definition available. + Details
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Namespace Prefix: | mbwm_
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Balance Type: | na
Period Type: | duration

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- 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. + 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 https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition The net cash inflow or outflow for the increase (decrease) in the beginning and end of period deposits balances. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3095-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 230 -Section 45 -Paragraph 1 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=123398031&loc=d3e60009-112784 + Details
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- Definition Amount of time deposit liabilities, including certificates of deposit, in denominations that meet or exceed the Federal Deposit Insurance Corporation (FDIC) insurance limit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 405 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=116652737&loc=d3e64164-112818 + Details
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