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Note 19 - Variable Interest Entities (Details Textual) |  |  | 12 Months Ended |
--- | --- | --- | --- | ---
Jan. 26, 2016 USD ($) | Jun. 01, 2014 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Number of Business Trusts |  |  | 5 |
Business Combination Debt Assumed Number of Trusts |  |  | 4 |
Fair Value Discount of Subordinated Debentures Related to Assumed Business Trusts at Time af Merger |  | $ 15,000,000.0 |  |
Amortization of Fair Value Discount Related to Subordinated Debentures of Assumed Business Trusts |  | $ 700,000 |  |
Amortization Period of Fair Value Discount Related to Subordinated Debentures of Assumed Business Trusts (Year) |  | 21 years 6 months |  |
Preferred Securities of Subsidiary Trust |  |  | $ 46,900,000 | $ 46,200,000
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust, Total |  |  | 48,958,000 | $ 48,244,000
Mercantile Bank Capital Trust I [Member] |  |  |  |
Preferred Securities of Subsidiary Trust | $ 32,000,000.0 |  | $ 21,000,000 |
Payments for Repurchase of Trust Preferred Securities | 11,000,000.0 |  |  |
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust, Total | 21,000,000.0 |  |  |
Fund [Member] | Mercantile Bank Capital Trust I [Member] |  |  |  |
Preferred Securities of Subsidiary Trust | $ 11,000,000.0 |  |  |
Five Business Trusts [Member] |  |  |  |
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage |  |  | 100.00% |

X
- Definition Represents the annual amortization of the fair value discount related to subordinated debentures of assumed business trusts over a period of time. + References No definition available. + Details
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- Definition Represents the amortization period of the fair value discount related to subordinated debentures of assumed business trusts. + References No definition available. + Details
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- Definition The number of trusts for which debt assumed in a business combination are payable to. + References No definition available. + Details
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- Definition Represents the fair value discount of subordinated debentures related to assumed business trusts at the time of the merger. + References No definition available. + Details
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- Definition Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878 + Details
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- Definition The cash outflow to reacquire preferred stocks issued by a business trust or other special purpose entity, mainly established by a bank holding entity, to third party investors. The trust's assets are deeply subordinated debentures of the bank holding entity. Most trust preferred securities are subject to a mandatory redemption upon the repayment of the debentures. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3291-108585 + Details
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- Definition Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 5A -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=123419778&loc=SL6759159-111685 + Details
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