XML 80 R71.htm IDEA: XBRL DOCUMENT
v3.23.3

Note 12 - Regulatory Matters (Details Textual) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions |  |  |  | 6 Months Ended | 9 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Jul. 13, 2023 | Apr. 13, 2023 | Jan. 12, 2023 | Sep. 30, 2023 | Sep. 30, 2023 | Dec. 31, 2022 | May 31, 2021 | Dec. 31, 2009
Preferred Securities of Subsidiary Trust |  |  |  | $ 47.4 | $ 47.4 | $ 46.9 |  |
Maximum Restricted Core Element Allowed in Tier One Capital Percent |  |  |  | 25.00% |  |  |  |
Maximum Level of Consolidated Aggregate Assets Allowing for Inclusion of Trust Preferred Securities in Tier One Capital |  |  |  |  |  |  |  | $ 15,000.0
Trust Preferred Securities Included in Tier One Capital |  |  |  | $ 47.4 | $ 47.4 | $ 46.9 |  |
Capital Conservation Buffer |  |  |  | 2.50% | 2.50% |  |  |
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy to Risk Weighted Assets |  |  |  | 0.07 | 0.07 |  |  |
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets |  |  |  | 0.085 | 0.085 |  |  |
Capital Required for Capital Adequacy to Risk Weighted Assets |  |  |  | 0.105 | 0.105 |  |  |
Common Stock, Dividends, Per Share, Declared (in dollars per share) | $ 0.34 | $ 0.33 | $ 0.33 |  |  |  |  |
Stock Repurchase Program, Remaining Authorized Repurchase Amount |  |  |  | $ 6.8 | $ 6.8 |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  |  |  |  | $ 20.0 |
Stock Repurchased During Period, Shares (in shares) |  |  |  |  | 0 |  |  |

X
- Definition An additional amount held in risk-based capital designed to ensure that banks build up capital buffers outside periods of stress which can be drawn down as losses are incurred. The requirement is based on simple capital conservation rules designed to avoid breaches of minimum capital requirements. + References No definition available. + Details
Name: | mbwm_CapitalConservationBuffer
Namespace Prefix: | mbwm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The minimum common equity tier one capital ratio (common equity tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References No definition available. + Details
Name: | mbwm_CommonEquityTier1RiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix: | mbwm_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition The maximum level of consolidated aggregate assets allowing for inclusion of trust preferred securities in Tier 1 Capital under the Dodd-Frank Act. + References No definition available. + Details
Name: | mbwm_MaximumLevelOfConsolidatedAggregateAssetsAllowingForInclusionOfTrustPreferredSecuritiesInTierOneCapital
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The maximum amount of restricted core elements allowed in tier one capital expressed as a percent. + References No definition available. + Details
Name: | mbwm_MaximumRestrictedCoreElementAllowedInTierOneCapitalPercent
Namespace Prefix: | mbwm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Trust preferred securities possesses characteristics of both equity and debt issues and are generally issued by bank holding companies. + References No definition available. + Details
Name: | mbwm_PreferredSecuritiesOfSubsidiaryTrust
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Trust preferred securities held by the trust that are included in Tier One Capital and subject to certain limitations. + References No definition available. + Details
Name: | mbwm_TrustPreferredSecuritiesIncludedInTierOneCapital
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B + Details
Name: | us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1 + Details
Name: | us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 10 -Topic 505 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481112/505-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481004/946-505-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(4)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(i)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_StockRepurchasedDuringPeriodShares
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Ratio of minimum Tier 1 risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B + Details
Name: | us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant