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Securities (Details Textual) (USD $) | 12 Months Ended
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Dec. 31, 2012 DebtSecurities MutualFund | Dec. 31, 2011 DebtSecurities | Dec. 31, 2010
Securities (Textual) [Abstract] |  |  |
Fair value of debt securities with unrealized losses | $ 33,555,000 | $ 19,291,000 |
Aggregate depreciation of securities with unrealized losses | 388,000 | 59,000 |
Available for sale Securities | 138,314,000 | 172,992,000 |
Securities (Additional Textual) [Abstract] |  |  |
Number of mutual funds with unrealized gains | 1 |  |
Fair Value of Debt and Equity Securities with Unrealized Gains | 85,500,000 |  |
Aggregate appreciation of securities with unrealized gains | 4,038,000 | 5,893,000 |
Aggregate appreciation as a percentage of total amortized cost of securities | 3.00% |  |
Amortized cost of municipal bonds transferred from held to maturity to available for sale |  |  | 39,200,000
Net unrealized gain at the date of transfer amounted | 0 | 0 | 274,000
Number of bonds sold | 0 | 0 |
Total securities of specific issuer, other than U.S. Government and its agencies, maximum percentage of stockholders' equity | 10.00% |  |
Nontaxable Municipal Bonds [Member] |  |  |
Securities (Textual) [Abstract] |  |  |
Municipal bonds with an aggregate book value |  |  | 20,000,000
Debt securities [Member] |  |  |
Securities (Textual) [Abstract] |  |  |
Number of debt securities with unrealized losses | 22 |  |
Fair value of debt securities with unrealized losses | 33,600,000 |  |
Aggregate depreciation of securities with unrealized losses | 400,000 |  |
Aggregate depreciation as a percentage of total amortized cost of securities | 0.30% |  |
Number of debt securities with unrealized gains | 187 |  |
State of Michigan and all its political subdivisions [Member] |  |  |
Securities (Textual) [Abstract] |  |  |
Amortized cost of securities | 23,400,000 | 30,500,000 |
Available for sale Securities | 24,600,000 | 31,700,000 |
U.S. Government agency debt obligations and mortgage-backed securities [Member] |  |  |
Securities (Textual) [Abstract] |  |  |
Carrying value of securities pledged to secure repurchase agreements and letters of credit issued | $ 83,800,000 | $ 109,000,000 |

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- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized 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 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 + Details
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