XML 69 R52.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Deposits - Components of Outstanding Balances and Percentage Change in Deposits (Detail) (USD $) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2013 | Dec. 31, 2012
Deposits By Component Alternative [Abstract] |  |
Noninterest-bearing demand | $ 216,055,000 | $ 190,241,000
Interest-bearing checking | 195,964,000 | 188,057,000
Money market | 136,363,000 | 144,479,000
Savings | 52,993,000 | 56,454,000
Time, under $100,000 | 45,146,000 | 51,730,000
Time, $100,000 and over | 257,651,000 | 234,430,000
Total Local Deposits | 904,172,000 | 865,391,000
Out-of-area interest-bearing checking | 0 | 21,967,000
Out-of-area time, under $100,000 | 4,672,000 | 7,706,000
Out-of-area time, $100,000 and over | 212,665,000 | 240,140,000
Total out-of-area deposits | 217,337,000 | 269,813,000
Total deposits | $ 1,121,509,000 | $ 1,135,204,000
Percentage of Noninterest-bearing demand | 19.30% | 16.80%
Percentage of Interest-bearing checking | 17.50% | 16.50%
Percentage of Money market | 12.10% | 12.70%
Percentage of Savings | 4.70% | 5.00%
Percentage of time, under $100,000 | 4.00% | 4.60%
Percentage of time, $100,000 and over | 23.00% | 20.60%
Percentage of total local deposits | 80.60% | 76.20%
Percentage of out-of-area interest-bearing checking | 0.00% | 1.90%
Percentage of out-of-area time, under $100,000 | 0.40% | 0.70%
Percentage of out-of-area time, $100,000 and over | 19.00% | 21.20%
Aggregate percentage of out-of-area deposits | 19.40% | 23.80%
Aggregate percentage of total deposits | 100.00% | 100.00%
Percentage of Increase or (Decrease) in Noninterest-bearing demand | 13.60% |
Percentage of Increase or (Decrease) of Interest-bearing checking Deposits | 4.20% |
Percentage of Increase or (Decrease) of Money market Deposits | (5.60%) |
Percentage of Increase or (Decrease) of Savings Deposits | (6.10%) |
Percentage of Increase or (Decrease) in Time, under $100,000 | (12.70%) |
Percentage of Increase or (Decrease) in Time, $100,000 and over | 9.90% |
Percentage of Increase or (Decrease) in Total Local Deposits | 4.50% |
Percentage of Increase or (Decrease) in out-of-area interest-bearing checking |  |
Percentage of Increase or (Decrease) in out-of- area time, under $100,000 | (39.40%) |
Percentage Increase or (Decrease) in out-of-area time, $100,000 and over | (11.40%) |
Aggregate Percentage Increase or (Decrease) in out-of-area deposits | (19.40%) |
Aggregate Percentage Increase or (Decrease) in Total Deposits | (1.20%) |

X
- Definition Aggregate percentage increase or decrease in total deposits. + References No definition available. + Details
Name: | mbwm_AggregateIncreaseOrDecreaseInPercentageOfDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate local deposit liabilities. + References No definition available. + Details
Name: | mbwm_AggregateLocalDepositLiabilities
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Aggregate out of area time deposits. + References No definition available. + Details
Name: | mbwm_AggregateOutOfAreaTimeDeposits
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate percentage increase or decrease in local deposits. + References No definition available. + Details
Name: | mbwm_AggregatePercentageIncreaseOrDecreaseInLocalDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate percentage increase or decrease in out-of-area deposits. + References No definition available. + Details
Name: | mbwm_AggregatePercentageIncreaseOrDecreaseInOutOfAreaDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate percentage of total deposits. + References No definition available. + Details
Name: | mbwm_AggregatePercentageOfDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate percentage of local deposits. + References No definition available. + Details
Name: | mbwm_AggregatePercentageOfLocalDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate percentage of out-of-area deposits. + References No definition available. + Details
Name: | mbwm_AggregatePercentageOfOutOfAreaDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Out of area interest bearing checking. + References No definition available. + Details
Name: | mbwm_OutOfAreaInterestBearingChecking
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Out of area time equal to greater than 100000. + References No definition available. + Details
Name: | mbwm_OutOfAreaTimeEqualToGreaterThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Out of area time less than 100000. + References No definition available. + Details
Name: | mbwm_OutOfAreaTimeLessThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage of increase or decrease in noninterest-bearing demand deposits. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseInNonInterestBearingDemandDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease in out of area interest bearing checking. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseInOutOfAreaInterestBearingChecking
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease in out of area time equal to greater than 100000. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseInOutOfAreaTimeEqualToGreaterThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease in out of area time less than 100000. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseInOutOfAreaTimeLessThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease in time deposits, $100,000 and over. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseInTimeDepositsEqualToGreaterThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease in time deposits less than $100,000. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseInTimeDepositsLessThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease of interest-bearing checking deposits. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseOfInterestBearingCheckingDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease of money market deposits. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseOfMoneyMarketDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of increase or decrease of savings deposits. + References No definition available. + Details
Name: | mbwm_PercentageOfIncreaseOrDecreaseOfSavingsDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of noninterest-bearing domestic demand deposit liabilities to total deposit liabilities. + References No definition available. + Details
Name: | mbwm_PercentageOfNonInterestBearingDomesticDepositsToDepositsDemand
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of out-of-area interest- bearing checking. + References No definition available. + Details
Name: | mbwm_PercentageOfOutOfAreaInterestBearingChecking
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of out of area time less than 100000. + References No definition available. + Details
Name: | mbwm_PercentageOfOutOfAreaTimeLessThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of time deposits equal to greater than 100000 to total deposit liabilities. + References No definition available. + Details
Name: | mbwm_PercentageOfTimeDepositsEqualToGreaterThanHundredThousandsToDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of time deposits less than 100000 to total deposit liabilities. + References No definition available. + Details
Name: | mbwm_PercentageOfTimeDepositsLessThanHundredThousandsToDeposits
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage out of area time equal to greater than 100000. + References No definition available. + Details
Name: | mbwm_PercentageOutOfAreaTimeEqualToGreaterThanHundredThousands
Namespace Prefix: | mbwm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 9 + Details
Name: | us-gaap_Deposits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Amount of interest-bearing domestic checking deposit liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 9 + Details
Name: | us-gaap_InterestBearingDomesticDepositChecking
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of interest-bearing domestic money market demand account deposit liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 9 + Details
Name: | us-gaap_InterestBearingDomesticDepositMoneyMarket
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of interest-bearing domestic savings deposit liabilities. Saving deposits bear interest and have no stated maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 9 + Details
Name: | us-gaap_InterestBearingDomesticDepositSavings
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of money in noninterest-bearing domestic accounts that entitle the depositor to withdraw funds at any time without prior notice, also known as demand deposits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 9 + Details
Name: | us-gaap_NoninterestBearingDomesticDepositDemand
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage of interest-bearing domestic checking demand deposit liabilities to total deposit liabilities. + References No definition available. + Details
Name: | us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsChecking
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of interest-bearing domestic money market demand account deposit liabilities to total deposit liabilities. + References No definition available. + Details
Name: | us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsMoneyMarket
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of interest-bearing domestic savings deposit liabilities to total deposit liabilities. + References No definition available. + Details
Name: | us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsSavings
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The aggregate amount of domestic time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 405 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6479006&loc=d3e64164-112818 + Details
Name: | us-gaap_TimeDeposits100000OrMoreDomestic
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The aggregate amount of domestic or foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000. + References No definition available. + Details
Name: | us-gaap_TimeDepositsLessThan100000
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant