Summary of Significant Accounting Policies	6 Months Ended
Jun. 30, 2011
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies Basis of Presentation — FirstMerit Corporation (“the Parent Company”) is a bank holding company whose principal asset is the common stock of its wholly-owned subsidiary, FirstMerit Bank, N. A. (the “Bank”). The Parent Company’s other subsidiaries include Citizens Savings Corporation of Stark County, FirstMerit Capital Trust I, FirstMerit Community Development Corporation, FirstMerit Risk Management, Inc., and FMT, Inc. All significant intercompany balances and transactions have been eliminated in consolidation. The accounting and reporting policies of FirstMerit Corporation and its subsidiaries (the “Corporation”) conform to generally accepted accounting principles in the United States of America (“U.S. GAAP”) and to general practices within the financial services industry. The consolidated balance sheet at December 31, 2010 has been derived from the audited consolidated financial statements at that date. The accompanying unaudited interim financial statements reflect all adjustments (consisting only of normally recurring adjustments) that are, in the opinion of FirstMerit Corporation’s Management (“Management”), necessary for a fair statement of the results for the interim periods presented. Certain information and note disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been omitted in accordance with the rules of the Securities and Exchange Commission (“SEC”). The unaudited consolidated financial statements of the Corporation as of June 30, 2011 and 2010 are not necessarily indicative of the results that may be achieved for the full fiscal year or for any future period. These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Corporation’s Annual Report on Form 10-K for the year ended December 31, 2010 (the “2010 Form 10-K”). Certain reclassifications of prior year’s amounts have been made to conform to the current year presentation. Such reclassifications had no effect on net earnings or equity. There have been no significant changes to the Corporation’s accounting policies as disclosed in the Annual Report on Form 10-K for the year ended December 31, 2010. In preparing these accompanying unaudited interim consolidated financial statements, subsequent events were evaluated through the time the consolidated financial statements were issued. No material subsequent events have occurred requiring recognition in the consolidated financial statements or disclosure in the notes to the consolidated financial statements. Recently Adopted and Issued Accounting Standards - FASB ASU 2010-06, Improving Disclosures about Fair Value Measurements. The Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2010-06 to amend ASC 820, Fair Value Measurement and Disclosures (“ASC 820”), to require additional disclosures regarding fair value measurements. Specifically, the ASU requires disclosure of the amounts of significant transfers between Level 1 and Level 2 of the fair value hierarchy and the reasons for these transfers; the reasons for any transfers in or out of Level 3; and information in the reconciliation of recurring Level 3 measurements about gross purchases, sales, issuances and settlements. Except for the requirement to disclose purchases, sales, issuances and settlements in the reconciliation of recurring Level 3 measurements on a gross basis, all the amendments to ASC 820 made by ASU 2010-06 were effective for the Corporation on January 1, 2010. The requirement to separately disclose purchases, sales, issuances and settlements of recurring Level 3 measurements was effective for the Corporation as of January 1, 2011. All required disclosures are incorporated into Note 11 (Fair Value Measurement). FASB ASU 2010-20, Disclosures about the Credit Quality of Financing Receivables and the Allowance for Credit Losses. In July 2010, the FASB issued ASU 2010-20, which requires new qualitative and quantitative disclosures on the allowance for credit losses, credit quality, impaired loans, modifications and nonaccrual and past due financing receivables. The guidance requires that an entity provide disclosures facilitating financial statement users’ evaluation of the nature of credit risk inherent in the entity’s portfolio of financing receivables (i.e., loans), how that risk is analyzed and assessed in arriving at the allowance for credit losses, and the changes and reasons for those changes in the allowance for credit losses. These required disclosures are to be presented on a disaggregated basis at the portfolio segment and the class of financing receivables level. As it relates to disclosures as of the end of a reporting period, ASU 2010-20 was effective for the Corporation as of December 31, 2010. Disclosures that relate to activity during a reporting period were required for the Corporation in the period beginning January 1, 2011 and are incorporated into Note 4 (Loans) and Note 5 (Allowance for Loan Losses). In January 2011, the FASB temporarily deferred the effective date for disclosures about troubled debt restructurings under ASU 2010-20. See ASU 2011-2 below which requires disclosures about troubled debt restructurings under ASU 2010-20 on a prospective basis beginning in the quarter ended September 30, 2011. FASB ASU 2010-28, When to Perform Step 2 of the Goodwill Impairment Test for Reporting Units with Zero or Negative Carrying Amounts. In December 2010, the FASB issued ASU 2010-28, which modifies Step 1 of the goodwill impairment test under ASC 350, Intangibles-Goodwill and Other (“ASC 350”), for reporting units with zero or negative carrying amounts. For those reporting units, an entity is required to perform Step 2 of the goodwill impairment test if it is more likely than not that a goodwill impairment exists. In determining whether it is more likely than not that a goodwill impairment exists, an entity should consider whether there are any adverse qualitative factors (as defined in ASC 350) indicating that an impairment may exist. This guidance was effective for the Corporation as of January 1, 2011. The adoption of ASU 2010-28 did not have an impact on the Corporation’s consolidated financial statements. FASB ASU 2010-29, Disclosure of Supplementary Pro Forma Information for Business Combinations. In December 2010, the FASB issued ASU 2010-29, which clarifies that if a public entity presents comparative financial statements, the entity should disclose revenue and earnings of the combined entity as though the business combination(s) that occurred during the current year had occurred as of the beginning of the comparable prior annual reporting period only. ASU 2010-29 is effective for the Corporation prospectively for business combinations for which the acquisition date is on or after the January 1, 2011. The Corporation has had no acquisitions subsequent to January 1, 2011. FASB ASU 2011-02, A Creditor’s Determination of Whether a Restructuring Is a Troubled Debt Restructuring. In April 2011, the FASB issued ASU 2011-02, which provides additional guidance to help creditors in determining whether a creditor has granted a concession and whether a debtor is experiencing financial difficulties for purposes of determining whether a restructuring constitutes a troubled debt restructuring. The amendments in this update are effective for the Corporation beginning in the quarter ended September 30, 2011 and are to be applied retrospectively to January 1, 2011. In addition, the modification disclosures described in ASU 2010-20, which were subsequently deferred by ASU 2011-01, Deferral of the Effective Date of Disclosures about Troubled Debt Restructurings, will be effective on a prospective basis beginning in the quarter ended September 30, 2011. The Corporation has not completed evaluating the impact of ASU 2011-02 on its consolidated financial statements. FASB ASU 2011-03, Reconsideration of Effective Control for Repurchase Agreements. In April 2011, the FASB issued ASU 2011-03, which removes from the assessment of effective control (1) the criterion requiring the transferor to have the ability to repurchase or redeem the financial assets on substantially the agreed terms, even in the event of default by the transferee, and (2) the collateral maintenance implementation guidance related to that criterion. ASU 2011-03 is effective prospectively for all transactions or modifications of existing transactions that occur on or after January 1, 2012. The Corporation has not completed evaluating the impact of ASU 2011-03 on its consolidated financial statements. FASB ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs. In May 2011, the FASB issued ASU 2011-04. The amendments in this update result in common fair value measurement and disclosure requirements in U.S. GAAP and International Financial Reporting Standards (“IFRSs”). Consequently, the amendments change the wording used to describe many of the requirements in U.S. GAAP for measuring fair value and for disclosing information about fair value measurements. For many of the requirements, the FASB does not intend for the amendments in this update to result in a change in the application of the requirements in ASC 820. Some of the amendments clarify the FASB’s intent about the application of existing fair value measurement requirements. Other amendments change a particular principle or requirement for measuring fair value or for disclosing information about fair value measurements. ASU 2011-04 is effective for the Corporation on a prospective basis beginning in the quarter ended March 31, 2012. The Corporation has not completed evaluating the impact of ASU 2011-04 on its consolidated financial statements. FASB ASU 2011-05, Presentation of Comprehensive Income. In June 2011, the FASB issued ASU 2011-05, which provides entities with the option to present the total of comprehensive income, the components of net income, and the components of other comprehensive income either in a single continuous statement of comprehensive income or in two separate but consecutive statements. In both choices, an entity is required to present each component of net income along with total net income, each component of other comprehensive income, along with a total for other comprehensive income, and a total amount for comprehensive income. Regardless of whether an entity chooses to present comprehensive income in a single continuous statement or in two separate but consecutive statements, the entity is required to present on the face of the financial statements reclassification adjustments for items that are reclassified from other comprehensive income to net income in the statement(s) where the components of net income and the components of other comprehensive income are presented. This update is effective on a retrospective basis beginning in the quarter ended March 31, 2012. As the Corporation currently reports comprehensive income in a single continuous statement with all of the components required by ASU 2011-05, the adoption of this guidance will not have an impact on its consolidated financial statements.

1. Summary of Significant Accounting Policies

Basis of Presentation — FirstMerit Corporation (“the Parent Company”) is a bank holding company whose principal asset is the common stock of its wholly-owned subsidiary, FirstMerit Bank, N. A. (the “Bank”). The Parent Company’s other subsidiaries include Citizens Savings Corporation of Stark County, FirstMerit Capital Trust I, FirstMerit Community Development Corporation, FirstMerit Risk Management, Inc., and FMT, Inc. All significant intercompany balances and transactions have been eliminated in consolidation.

The accounting and reporting policies of FirstMerit Corporation and its subsidiaries (the “Corporation”) conform to generally accepted accounting principles in the United States of America (“U.S. GAAP”) and to general practices within the financial services industry.

The consolidated balance sheet at December 31, 2010 has been derived from the audited consolidated financial statements at that date. The accompanying unaudited interim financial statements reflect all adjustments (consisting only of normally recurring adjustments) that are, in the opinion of FirstMerit Corporation’s Management (“Management”), necessary for a fair statement of the results for the interim periods presented. Certain information and note disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been omitted in accordance with the rules of the Securities and Exchange Commission (“SEC”). The unaudited consolidated financial statements of the Corporation as of June 30, 2011 and 2010 are not necessarily indicative of the results that may be achieved for the full fiscal year or for any future period. These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Corporation’s Annual Report on Form 10-K for the year ended December 31, 2010 (the “2010 Form 10-K”). Certain reclassifications of prior year’s amounts have been made to conform to the current year presentation. Such reclassifications had no effect on net earnings or equity.

There have been no significant changes to the Corporation’s accounting policies as disclosed in the Annual Report on Form 10-K for the year ended December 31, 2010.

In preparing these accompanying unaudited interim consolidated financial statements, subsequent events were evaluated through the time the consolidated financial statements were issued. No material subsequent events have occurred requiring recognition in the consolidated financial statements or disclosure in the notes to the consolidated financial statements.

Recently Adopted and Issued Accounting Standards -

FASB ASU 2010-06, Improving Disclosures about Fair Value Measurements. The Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2010-06 to amend ASC 820, Fair Value Measurement and Disclosures (“ASC 820”), to require additional disclosures regarding fair value measurements. Specifically, the ASU requires disclosure of the amounts of significant transfers between Level 1 and Level 2 of the fair value hierarchy and the reasons for these transfers; the reasons for any transfers in or out of Level 3; and information in the reconciliation of recurring Level 3 measurements about gross purchases, sales, issuances and settlements. Except for the requirement to disclose purchases, sales, issuances and settlements in the reconciliation of recurring Level 3 measurements on a gross basis, all the amendments to ASC 820 made by ASU 2010-06 were effective for the Corporation on January 1, 2010. The requirement to separately disclose purchases, sales, issuances and settlements of recurring Level 3 measurements was effective for the Corporation as of January 1, 2011. All required disclosures are incorporated into Note 11 (Fair Value Measurement).

FASB ASU 2010-20, Disclosures about the Credit Quality of Financing Receivables and the Allowance for Credit Losses. In July 2010, the FASB issued ASU 2010-20, which requires new qualitative and quantitative disclosures on the allowance for credit losses, credit quality, impaired loans, modifications and nonaccrual and past due financing receivables. The guidance requires that an entity provide disclosures facilitating financial statement users’ evaluation of the nature of credit risk inherent in the entity’s portfolio of financing receivables (i.e., loans), how that risk is analyzed and assessed in arriving at the allowance for credit losses, and the changes and reasons for those changes in the allowance for credit losses. These required disclosures are to be presented on a disaggregated basis at the portfolio segment and the class of financing receivables level. As it relates to disclosures as of the end of a reporting period, ASU 2010-20 was effective for the Corporation as of December 31, 2010. Disclosures that relate to activity during a reporting period were required for the Corporation in the period beginning January 1, 2011 and are incorporated into Note 4 (Loans) and Note 5 (Allowance for Loan Losses). In January 2011, the FASB temporarily deferred the effective date for disclosures about troubled debt restructurings under ASU 2010-20. See ASU 2011-2 below which requires disclosures about troubled debt restructurings under ASU 2010-20 on a prospective basis beginning in the quarter ended September 30, 2011.

FASB ASU 2010-28, When to Perform Step 2 of the Goodwill Impairment Test for Reporting Units with Zero or Negative Carrying Amounts. In December 2010, the FASB issued ASU 2010-28, which modifies Step 1 of the goodwill impairment test under ASC 350, Intangibles-Goodwill and Other (“ASC 350”), for reporting units with zero or negative carrying amounts. For those reporting units, an entity is required to perform Step 2 of the goodwill impairment test if it is more likely than not that a goodwill impairment exists. In determining whether it is more likely than not that a goodwill impairment exists, an entity should consider whether there are any adverse qualitative factors (as defined in ASC 350) indicating that an impairment may exist. This guidance was effective for the Corporation as of January 1, 2011. The adoption of ASU 2010-28 did not have an impact on the Corporation’s consolidated financial statements.

FASB ASU 2010-29, Disclosure of Supplementary Pro Forma Information for Business Combinations. In December 2010, the FASB issued ASU 2010-29, which clarifies that if a public entity presents comparative financial statements, the entity should disclose revenue and earnings of the combined entity as though the business combination(s) that occurred during the current year had occurred as of the beginning of the comparable prior annual reporting period only. ASU 2010-29 is effective for the Corporation prospectively for business combinations for which the acquisition date is on or after the January 1, 2011. The Corporation has had no acquisitions subsequent to January 1, 2011.

FASB ASU 2011-02, A Creditor’s Determination of Whether a Restructuring Is a Troubled Debt Restructuring. In April 2011, the FASB issued ASU 2011-02, which provides additional guidance to help creditors in determining whether a creditor has granted a concession and whether a debtor is experiencing financial difficulties for purposes of determining whether a restructuring constitutes a troubled debt restructuring. The amendments in this update are effective for the Corporation beginning in the quarter ended September 30, 2011 and are to be applied retrospectively to January 1, 2011. In addition, the modification disclosures described in ASU 2010-20, which were subsequently deferred by ASU 2011-01, Deferral of the Effective Date of Disclosures about Troubled Debt Restructurings, will be effective on a prospective basis beginning in the quarter ended September 30, 2011. The Corporation has not completed evaluating the impact of ASU 2011-02 on its consolidated financial statements.

FASB ASU 2011-03, Reconsideration of Effective Control for Repurchase Agreements. In April 2011, the FASB issued ASU 2011-03, which removes from the assessment of effective control (1) the criterion requiring the transferor to have the ability to repurchase or redeem the financial assets on substantially the agreed terms, even in the event of default by the transferee, and (2) the collateral maintenance implementation guidance related to that criterion. ASU 2011-03 is effective prospectively for all transactions or modifications of existing transactions that occur on or after January 1, 2012. The Corporation has not completed evaluating the impact of ASU 2011-03 on its consolidated financial statements.

FASB ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs. In May 2011, the FASB issued ASU 2011-04. The amendments in this update result in common fair value measurement and disclosure requirements in U.S. GAAP and International Financial Reporting Standards (“IFRSs”). Consequently, the amendments change the wording used to describe many of the requirements in U.S. GAAP for measuring fair value and for disclosing information about fair value measurements. For many of the requirements, the FASB does not intend for the amendments in this update to result in a change in the application of the requirements in ASC 820. Some of the amendments clarify the FASB’s intent about the application of existing fair value measurement requirements. Other amendments change a particular principle or requirement for measuring fair value or for disclosing information about fair value measurements. ASU 2011-04 is effective for the Corporation on a prospective basis beginning in the quarter ended March 31, 2012. The Corporation has not completed evaluating the impact of ASU 2011-04 on its consolidated financial statements.

FASB ASU 2011-05, Presentation of Comprehensive Income. In June 2011, the FASB issued ASU 2011-05, which provides entities with the option to present the total of comprehensive income, the components of net income, and the components of other comprehensive income either in a single continuous statement of comprehensive income or in two separate but consecutive statements. In both choices, an entity is required to present each component of net income along with total net income, each component of other comprehensive income, along with a total for other comprehensive income, and a total amount for comprehensive income. Regardless of whether an entity chooses to present comprehensive income in a single continuous statement or in two separate but consecutive statements, the entity is required to present on the face of the financial statements reclassification adjustments for items that are reclassified from other comprehensive income to net income in the statement(s) where the components of net income and the components of other comprehensive income are presented. This update is effective on a retrospective basis beginning in the quarter ended March 31, 2012. As the Corporation currently reports comprehensive income in a single continuous statement with all of the components required by ASU 2011-05, the adoption of this guidance will not have an impact on its consolidated financial statements.