Represents the percentage of stock award types issued during the period.

No definition available.

Name:	fmbh_PercentageOfAwardsIssued
Namespace Prefix:	fmbh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of Awards Issued to Retirement Eligible Employees

+ References

No definition available.

+ Details

Name:	fmbh_PercentageOfAwardsIssuedToRetirementEligible
Namespace Prefix:	fmbh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_StockCompensationPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stock Incentive Plan (Details)	12 Months Ended
Stock Incentive Plan (Details)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	300,000
Share-based Compensation Arrangement by Share-based Payment Award, Terms of Award	10-year
Options, Grants in Period, Gross	0	0	0
RSA/RSU, Grants in Period, Gross	19,377	14,054	15,162
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, Grants in Period, Gross				59,500
Stock Unit Awards and Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSA/RSU, Grants in Period, Gross	19,377	14,054	15,162
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awards Issued	50.00%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awards Issued	50.00%
Percentage of Awards Issued to Retirement Eligible	100.00%