XML 66 R66.htm IDEA: XBRL DOCUMENT
v3.3.0.814

Note 12 - Regulatory Matters (Details) - Actual Capital Levels and Minimum Levels - USD ($) $ in Thousands | Sep. 30, 2015 | Dec. 31, 2014
--- | --- | ---
Consolidated Entities [Member] |  |
Total capital (to risk weighted assets) |  |
Total capital (to risk weighted assets), actual amount | $ 341,029 | $ 334,793
Total capital (to risk weighted assets), actual ratio | 13.60% | 14.40%
Total capital (to risk weighted assets), minimum required for capital adequacy purposes amount | $ 200,894 | $ 185,553
Total capital (to risk weighted assets), minimum required for capital adequacy purposes ratio | 8.00% | 8.00%
Total capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations amount |  |
Total capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations, ratio |  |
Tier 1 capital (to risk weighted assets) |  |
Tier 1 capital (to risk weighted assets), actual amount | $ 324,911 | $ 314,752
Tier 1 capital (to risk weighted assets), actual ratio | 12.90% | 13.60%
Tier 1 capital (to risk weighted assets), minimum required for capital adequacy purposes amount | $ 150,671 | $ 92,777
Tier 1 capital (to risk weighted assets), minimum required for capital adequacy purposes ratio | 6.00% | 4.00%
Tier 1 capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations amount |  |
Tier 1 capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations, ratio |  |
Common equity tier 1 (to risk weighted assets) |  |
Common equity tier 1 (to risk weighted assets), actual amount | $ 275,395 |
Common equity tier 1 (to risk weighted assets), actual ratio | 11.00% |
Common equity tier 1 (to risk weighted assets), minimum required for capital adequacy purposes amount | $ 113,156 |
Common equity tier 1 (to risk weighted assets), minimum required for capital adequacy purposes ratio | 4.50% |
Common equity tier 1 (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations amount |  |
Common equity tier 1 (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations, ratio |  |
Tier 1 capital (to average assets) |  |
Tier 1 capital (to average assets), actual amount | $ 324,911 | $ 314,752
Tier 1 capital (to average assets), actual ratio | 11.50% | 11.20%
Tier 1 capital (to average assets), minimum required for capital adequacy purposes amount | $ 112,825 | $ 112,949
Tier 1 capital (to risk average assets), minimum required for capital adequacy purposes ratio | 4.00% | 4.00%
Tier 1 capital (to risk average assets), minimum required to be well capitalized under prompt corrective action regulations amount |  |
Tier 1 capital (to risk average assets), minimum required to be well capitalized under prompt corrective action regulations, ratio |  |
Bank [Member] |  |
Total capital (to risk weighted assets) |  |
Total capital (to risk weighted assets), actual amount | $ 343,288 | $ 332,749
Total capital (to risk weighted assets), actual ratio | 13.70% | 14.40%
Total capital (to risk weighted assets), minimum required for capital adequacy purposes amount | $ 200,989 | $ 185,309
Total capital (to risk weighted assets), minimum required for capital adequacy purposes ratio | 8.00% | 8.00%
Total capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations amount | $ 251,236 | $ 231,636
Total capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations, ratio | 10.00% | 10.00%
Tier 1 capital (to risk weighted assets) |  |
Tier 1 capital (to risk weighted assets), actual amount | $ 327,169 | $ 312,708
Tier 1 capital (to risk weighted assets), actual ratio | 13.00% | 13.50%
Tier 1 capital (to risk weighted assets), minimum required for capital adequacy purposes amount | $ 150,742 | $ 92,655
Tier 1 capital (to risk weighted assets), minimum required for capital adequacy purposes ratio | 6.00% | 4.00%
Tier 1 capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations amount | $ 200,989 | $ 138,982
Tier 1 capital (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations, ratio | 8.00% | 6.00%
Common equity tier 1 (to risk weighted assets) |  |
Common equity tier 1 (to risk weighted assets), actual amount | $ 327,169 |
Common equity tier 1 (to risk weighted assets), actual ratio | 13.00% |
Common equity tier 1 (to risk weighted assets), minimum required for capital adequacy purposes amount | $ 113,057 |
Common equity tier 1 (to risk weighted assets), minimum required for capital adequacy purposes ratio | 4.50% |
Common equity tier 1 (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations amount | $ 163,304 |
Common equity tier 1 (to risk weighted assets), minimum required to be well capitalized under prompt corrective action regulations, ratio | 6.50% |
Tier 1 capital (to average assets) |  |
Tier 1 capital (to average assets), actual amount | $ 327,169 | $ 312,708
Tier 1 capital (to average assets), actual ratio | 11.60% | 11.10%
Tier 1 capital (to average assets), minimum required for capital adequacy purposes amount | $ 112,914 | $ 112,856
Tier 1 capital (to risk average assets), minimum required for capital adequacy purposes ratio | 4.00% | 4.00%
Tier 1 capital (to risk average assets), minimum required to be well capitalized under prompt corrective action regulations amount | $ 141,142 | $ 141,070
Tier 1 capital (to risk average assets), minimum required to be well capitalized under prompt corrective action regulations, ratio | 5.00% | 5.00%

X
- Definition Common equity tier 1 risk based capital as defined in the regulations. + References No definition available. + Details
Name: | mbwm_CommonEquityTier1RiskBasedCapital
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum amount of common equity tier 1 risk based capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References No definition available. + Details
Name: | mbwm_CommonEquityTier1RiskBasedCapitalRequiredForCapitalAdequacy
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of common equity tier 1 risk based capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action. + References No definition available. + Details
Name: | mbwm_CommonEquityTier1RiskBasedCapitalRequiredToBeWellCapitalized
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Common equity tier 1 capital ratio (common equity tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. + References No definition available. + Details
Name: | mbwm_CommonEquityTier1RiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Common equity tier 1 capital divided by risk weighted assets as defined in the regulations. + References No definition available. + Details
Name: | mbwm_CommonEquityTier1RiskBasedCapitalToRiskWeightedAssets
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | mbwm_CommonEquityTier1ToRiskWeightedAssetsAbstract
Namespace Prefix: | mbwm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | mbwm_Tier1CapitalToAverageAssetsAbstract
Namespace Prefix: | mbwm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | mbwm_Tier1CapitalToRiskWeightedAssetsAbstract
Namespace Prefix: | mbwm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | mbwm_TotalCapitalToRiskWeightedAssetsAbstract
Namespace Prefix: | mbwm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of total capital as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998 + Details
Name: | us-gaap_Capital
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_CapitalRequiredForCapitalAdequacy
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
Name: | us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_CapitalRequiredToBeWellCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total Capital divided by risk weighted assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_CapitalToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 + Details
Name: | us-gaap_TierOneLeverageCapital
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Tier 1 Leverage Capital divided by average assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 + Details
Name: | us-gaap_TierOneLeverageCapitalToAverageAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Tier 1 Risk Based Capital as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 + Details
Name: | us-gaap_TierOneRiskBasedCapital
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 + Details
Name: | us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
Name: | us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Tier 1 capital divided by risk weighted assets as defined by regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 + Details
Name: | us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=us-gaap_ConsolidatedEntitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mbwm_BankMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |