Collateral Dependant Impaired and Non Accrual Loans Carrying Amount

No definition available.

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- Definition

Determination Of Specific Allowance For Loan Losses

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Fair Value of Mortgage Servicing Rights

+ References

No definition available.

+ Details

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- Definition

Impaired and non accrual loans fair value disclosure.

+ References

No definition available.

+ Details

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- Definition

Impaired Collateral Dependant Loans, Recorded Investment

+ References

No definition available.

+ Details

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- Definition

Impairment of Covered Other Real Esate Owned

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Impairment of Noncovered Other Real Estate Owned

+ References

No definition available.

+ Details

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- Definition

Mortgage Servicing Rights.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Mortgage Servicing Rights Net Carrying balance

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Mortgage Servicing rights Valuation Allowance

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Nonrecurring Fair Value

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Nonrecurring Fair Value Measurements [Abstract]

+ References

No definition available.

+ Details

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- Definition

Other Real Estate Covered by loss Share.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

True Up Liability.

+ References

No definition available.

+ Details

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

- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a recurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Balance Type:	debit
Period Type:	instant

- Definition

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Period Type:	instant

- References

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Aggregation of the liabilities reported on the balance sheet measured at fair value on a recurring basis by the entity.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

+ Details

Name:	us-gaap_LoansHeldForSaleFairValueDisclosure
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Balance Type:	debit
Period Type:	instant

- Definition

The adjustment to the carrying value of the rights retained or purchased to service mortgages. These adjustments are made when the estimate of the fair value is changed. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying amount of other real estate not covered by loss sharing agreements not separately disclosed, including, but not limited to, real estate investments, real estate loans that qualify as investments in real estate, and premises that are no longer used in operations that may also be included in real estate owned. Excludes real estate assets taken in settlement of troubled loans through surrender or foreclosure by banks.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherRealEstateNonCovered
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Fair Value Measurement (Recurring and Nonrecurring Table) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Recurring Fair Value Measurements
Available-for-sale	$ 3,967,735	$ 3,545,288
Accumulated Gross Unrealized Loss	57,027	52,631
Loans held for sale, Fair Value	5,472	13,428
Derivative Asset, Fair Value, Gross Asset	58,107	55,197
Total Assets, Fair Value Disclosure, Recurring	4,031,314	3,613,913
Derivative Liability, Fair Value, Gross Liability	52,745	55,439
True Up Liability	14,750	13,294
Total liabilities at fair value on a recurring basis	67,495	68,733
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	19,149	21,228	$ 23,041
Impaired and Non Accrual Loans Fair Value Disclosure	71,428	56,041
Other Real Estate, Non Covered	18,576	12,510
Other Real Estate Covered by Loss Share	365	3,614
Nonrecurring Fair Value	109,518	93,393
Mortgage Servicing Rights	18,937	22,011	22,760	$ 21,316
Mortgage Servicing rights Valuation Allowance	(399)	(955)	(282)	$ (2,564)
MSRs, net carrying balance	18,538	21,056	22,478
Mortgage Servicing Rights (MSR) Impairment (Recovery)	(556)	673	$ (2,282)
Impaired Collateral Dependant Loans, Recorded Investment	84,300	60,300
Determination Of Specific Allowance For Loan Losses	(12,900)	(4,300)
Collateral Dependant Impaired and Non Accrual Loans Carrying Amount	71,400	56,000
Impairment of Other Real Estate Owned	4,500	2,600
Impairment of Covered Other Real Esate Owned	600	1,200
Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	49,368	49,941
Derivative Liability, Fair Value, Gross Liability	49,209	48,756
Interest Rate Swap \| Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	8,739	5,256
Derivative Liability, Fair Value, Gross Liability	3,536	6,683
Interest Rate Swap \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	48,920	48,366
Derivative Liability, Fair Value, Gross Liability	48,920	48,366
Mortgage Loan Commitments \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	149	1,408
Derivative Liability, Fair Value, Gross Liability	0	0
Forward Contracts \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	5	272
Foreign Exchange \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	299	167
Derivative Liability, Fair Value, Gross Liability	284	118
Marketable equity securities
Recurring Fair Value Measurements
Available-for-sale	2,821	2,974
Accumulated Gross Unrealized Loss	0	0
Total equity securities
Recurring Fair Value Measurements
Available-for-sale	2,821	2,974
Accumulated Gross Unrealized Loss	0
U.S. Treasury obligations
Recurring Fair Value Measurements
Available-for-sale	5,000
Accumulated Gross Unrealized Loss	1
U.S. Government agencies
Recurring Fair Value Measurements
Available-for-sale	2,498	2,482
Accumulated Gross Unrealized Loss	2	18
U.S. States and political subdivisions
Recurring Fair Value Measurements
Available-for-sale	192,795	227,342
Accumulated Gross Unrealized Loss	204	466
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	906,229	970,998
Accumulated Gross Unrealized Loss	5,454	3,218
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	172,109	103,403
Accumulated Gross Unrealized Loss	2,023	1,371
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	2,128,320	1,676,567
Accumulated Gross Unrealized Loss	30,147	26,225
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency
Recurring Fair Value Measurements
Available-for-sale	4	7
Accumulated Gross Unrealized Loss	0	0
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	216,319	222,334
Accumulated Gross Unrealized Loss	1,269	1,405
Corporate bonds
Recurring Fair Value Measurements
Available-for-sale	52,229	51,337
Accumulated Gross Unrealized Loss	9,481	10,315
Collateralized Loan Obligations
Recurring Fair Value Measurements
Available-for-sale	289,411	287,844
Accumulated Gross Unrealized Loss	8,446	9,613
Level 1
Recurring Fair Value Measurements
Available-for-sale	2,821	2,974
Loans held for sale, Fair Value	0	0
Derivative Asset, Fair Value, Gross Asset	0	0
Total Assets, Fair Value Disclosure, Recurring	2,821	2,974
Derivative Liability, Fair Value, Gross Liability	0	0
True Up Liability	0	0
Total liabilities at fair value on a recurring basis	0	0
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	0	0
Impaired and Non Accrual Loans Fair Value Disclosure	0	0
Other Real Estate, Non Covered	0	0
Other Real Estate Covered by Loss Share	0	0
Nonrecurring Fair Value	0	0
Level 1 \| Interest Rate Swap \| Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Level 1 \| Interest Rate Swap \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Level 1 \| Mortgage Loan Commitments \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Level 1 \| Forward Contracts \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability	0	0
Level 1 \| Foreign Exchange \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Level 1 \| Marketable equity securities
Recurring Fair Value Measurements
Available-for-sale	2,821
Level 1 \| Total equity securities
Recurring Fair Value Measurements
Available-for-sale		2,974
Level 1 \| U.S. Government agencies
Recurring Fair Value Measurements
Available-for-sale	0
Level 1 \| U.S. States and political subdivisions
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 1 \| Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 1 \| Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 1 \| Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 1 \| Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 1 \| Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 1 \| Corporate bonds
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 1 \| Collateralized Loan Obligations
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 2
Recurring Fair Value Measurements
Available-for-sale	3,623,270	3,203,127
Loans held for sale, Fair Value	5,472	13,428
Derivative Asset, Fair Value, Gross Asset	58,107	55,197
Total Assets, Fair Value Disclosure, Recurring	3,686,849	3,271,752
Derivative Liability, Fair Value, Gross Liability	52,745	55,439
True Up Liability	0	0
Total liabilities at fair value on a recurring basis	52,745	55,439
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	0	0
Impaired and Non Accrual Loans Fair Value Disclosure	0	0
Other Real Estate, Non Covered	0	0
Other Real Estate Covered by Loss Share	0	0
Nonrecurring Fair Value	0	0
Level 2 \| Interest Rate Swap \| Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	8,739	5,256
Derivative Liability, Fair Value, Gross Liability	3,536	6,683
Level 2 \| Interest Rate Swap \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	48,920	48,366
Derivative Liability, Fair Value, Gross Liability	48,920	48,366
Level 2 \| Mortgage Loan Commitments \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	149	1,408
Level 2 \| Forward Contracts \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability	5	272
Level 2 \| Foreign Exchange \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	299	167
Derivative Liability, Fair Value, Gross Liability	284	118
Level 2 \| Marketable equity securities
Recurring Fair Value Measurements
Available-for-sale	0
Level 2 \| Total equity securities
Recurring Fair Value Measurements
Available-for-sale		0
Level 2 \| U.S. Treasury obligations
Recurring Fair Value Measurements
Available-for-sale	5,000
Level 2 \| U.S. Government agencies
Recurring Fair Value Measurements
Available-for-sale	2,498	2,482
Level 2 \| U.S. States and political subdivisions
Recurring Fair Value Measurements
Available-for-sale	192,795	227,342
Level 2 \| Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	906,229	970,998
Level 2 \| Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	172,109	103,403
Level 2 \| Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	2,128,320	1,676,567
Level 2 \| Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency
Recurring Fair Value Measurements
Available-for-sale	0	1
Level 2 \| Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	216,319	222,334
Level 2 \| Corporate bonds
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 2 \| Collateralized Loan Obligations
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 3
Recurring Fair Value Measurements
Available-for-sale	341,644	339,187
Loans held for sale, Fair Value	0	0
Derivative Asset, Fair Value, Gross Asset	0	0
Total Assets, Fair Value Disclosure, Recurring	341,644	339,187
Derivative Liability, Fair Value, Gross Liability	0	0
True Up Liability	14,750	13,294
Total liabilities at fair value on a recurring basis	14,750	13,294
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	19,149	21,228
Impaired and Non Accrual Loans Fair Value Disclosure	71,428	56,041
Other Real Estate, Non Covered	18,576	12,510
Other Real Estate Covered by Loss Share	365	3,614
Nonrecurring Fair Value	109,518	93,393
Level 3 \| Interest Rate Swap \| Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Level 3 \| Interest Rate Swap \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Level 3 \| Mortgage Loan Commitments \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Level 3 \| Forward Contracts \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability	0	0
Level 3 \| Foreign Exchange \| Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Level 3 \| Marketable equity securities
Recurring Fair Value Measurements
Available-for-sale	0
Level 3 \| Total equity securities
Recurring Fair Value Measurements
Available-for-sale		0
Level 3 \| U.S. Government agencies
Recurring Fair Value Measurements
Available-for-sale	0
Level 3 \| U.S. States and political subdivisions
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 3 \| Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 3 \| Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 3 \| Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 3 \| Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency
Recurring Fair Value Measurements
Available-for-sale	4	6
Level 3 \| Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	0	0
Level 3 \| Corporate bonds
Recurring Fair Value Measurements
Available-for-sale		51,337
Level 3 \| Collateralized Loan Obligations
Recurring Fair Value Measurements
Available-for-sale	$ 289,411	$ 287,844