v2.4.0.6

Leases Lease Terms Details (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Operating Leased Assets [Line Items] |  |  |
Operating Leases, Rent Expense, Net | $ 1,293 | $ 1,331 | $ 884
Minimum [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Term of Lease | one year |  |
Renewal Term of Lease | one year |  |
Maximum [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Term of Lease | fifteen years |  |
Renewal Term of Lease | five years |  |

X
- Definition Number of years in Renewal Term of Lease + References No definition available. + Details
Name: | fmbh_RenewalTermOfLease
Namespace Prefix: | fmbh_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Length of Term of Lease + References No definition available. + Details
Name: | fmbh_TermOfLease
Namespace Prefix: | fmbh_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717 + Details
Name: | us-gaap_OperatingLeasesRentExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration