Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Subordinated Debt

No definition available.

Name:	fmer_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedSubordinatedDebt
Namespace Prefix:	fmer_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Variable Interest Entity-Aggregate Liquidation Amount Outstanding

+ References

No definition available.

+ Details

Name:	fmer_VariableInterestEntityAggregateLiquidationAmountOutstanding
Namespace Prefix:	fmer_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

States the lowest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateRangeFrom
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

States the highest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateRangeTo
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=fmer_CitizensRepublicBancorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=fmer_VIE1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=fmer_VIE2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Borrowed Funds (Narrative) (Details) (USD $)	12 Months Ended
Borrowed Funds (Narrative) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2014	Nov. 25, 2014	Apr. 12, 2013	Feb. 04, 2013
Debt Instrument [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	2,400,000,000	$ 5,100,000,000
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Interest Rate, Range from		1.11%
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Interest Rate, Range to		4.12%
Subordinate debentures \| Subordinated Notes Due 2026
Debt Instrument [Line Items]
Debt Instrument, Face Amount			250,000,000
Debt Instrument, Interest Rate, Stated Percentage			4.27%
Citizens Republic Bancorp
Debt Instrument [Line Items]
Debt Instrument, Face Amount					250,000,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Subordinated Debt				74,500,000
Citizens Republic Bancorp \| Subordinate debentures \| Subordinated Notes Due 2023
Debt Instrument [Line Items]
Debt Instrument, Face Amount					250,000,000
Debt Instrument, Interest Rate, Stated Percentage					4.35%
Citizens Republic Bancorp \| Maximum \| Junior Subordinated Debt \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	11.75%
VIE 2
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.10%
VIE 2 \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Variable Interest Entity-Aggregate Liquidation Amount Outstanding	25,800,000
Debt Instrument, Description of Variable Rate Basis	LIBOR
VIE 1
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Variable Interest Entity-Aggregate Liquidation Amount Outstanding	48,700,000