XML 62 R53.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Securities - Maturities of Securities and Their Weighted Average Yields (Detail) (USD $) | Dec. 31, 2013 | Dec. 31, 2012
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted Average Yield | 3.73% |
Amortized Cost | $ 139,487,000 | $ 134,664,000
Available for sale securities/Fair Value | 131,178,000 | 138,314,000
Due in one year or less [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted Average Yield | 5.32% |
Amortized Cost | 2,444,000 |
Available for sale securities/Fair Value | 2,494,000 |
Due from one to five years [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted Average Yield | 6.31% |
Amortized Cost | 1,018,000 |
Available for sale securities/Fair Value | 1,047,000 |
Due from five to ten years [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted Average Yield | 3.13% |
Amortized Cost | 32,373,000 |
Available for sale securities/Fair Value | 31,008,000 |
Due after ten years [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted Average Yield | 3.68% |
Amortized Cost | 89,810,000 |
Available for sale securities/Fair Value | 81,716,000 |
Mortgage-backed securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted Average Yield | 5.17% |
Amortized Cost | 12,456,000 | 20,182,000
Available for sale securities/Fair Value | 13,558,000 | 21,996,000
Mutual funds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted Average Yield | 2.32% |
Amortized Cost | 1,386,000 | 1,354,000
Available for sale securities/Fair Value | $ 1,355,000 | $ 1,405,000

X
- Definition Weighted average yield of securities portfolio. + References No definition available. + Details
Name: | mbwm_WeightedAverageYieldOfSecuritiesPortfolio
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration