XML 52 R37.htm IDEA: XBRL DOCUMENT
v3.20.4

Note 5 - Mortgage Loan Servicing (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2020
Notes Tables |
Mortgage Loans Serviced for Others [Table Text Block] |
|  | 2020 |  |  | 2019 |
Mortgage loan portfolios serviced for: |  |  |  |  |  |  |  |
Federal Home Loan Mortgage Corporation |  | $ | 1,030,211,000 |  |  | $ | 711,643,000 |
Federal Home Loan Bank |  |  | 8,717,000 |  |  |  | 15,317,000 |
Total mortgage loans serviced for others |  | $ | 1,038,928,000 |  |  | $ | 726,960,000 |
Servicing Asset at Amortized Cost [Table Text Block] |
|  | 2020 |  |  | 2019 |
Balance at beginning of year |  | $ | 4,652,000 |  |  | $ | 4,436,000 |
Additions |  |  | 6,467,000 |  |  |  | 1,962,000 |
Amortized to expense |  |  | (2,930,000 | ) |  |  | (1,746,000 | )
Balance at end of year |  | $ | 8,189,000 |  |  | $ | 4,652,000 |
Schedule of Mortgage Servicing Rights Future Amortization Expense [Table Text Block] |
2021 |  | $ | 1,724,000 |
2022 |  |  | 1,476,000 |
2023 |  |  | 1,241,000 |
2024 |  |  | 1,026,000 |
2025 |  |  | 834,000 |
Thereafter |  |  | 1,888,000 |

X
- Definition Tabular disclosure on mortgage loan portfolios serviced for others. + References No definition available. + Details
Name: | mbwm_MortgageLoansServicedForOthersTableTextBlock
Namespace Prefix: | mbwm_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the amount of amortization expense expected to be recorded in succeeding fiscal years for mortgage servicing rights. + References No definition available. + Details
Name: | mbwm_ScheduleOfMortgageServicingRightsFutureAmortizationExpenseTableTextBlock
Namespace Prefix: | mbwm_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of activity in the balance of servicing assets subsequently measured at amortized cost. Includes, but is not limited to, beginning and ending balances, additions, disposals, and amortization. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122739-111746 + Details
Name: | us-gaap_ScheduleOfServicingAssetsAtAmortizedValueTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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