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Securities - Additional Information (Detail) (USD $) | Sep. 30, 2013 Funds | Dec. 31, 2012
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Schedule of Available-for-sale Securities [Line Items] |  |
Number of mutual funds with unrealized losses | 1 |
Fair value of debt securities with unrealized losses | $ 78,035,000 | $ 33,555,000
Aggregate depreciation of securities with unrealized losses | (8,554,000) | (388,000)
Available for sale securities/Fair Value | 123,793,000 | 138,314,000
Total securities of specific issuer, other than U.S. Government and its agencies, maximum percentage of stockholders' equity | 10.00% |
Debt securities[Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Number of debt securities with unrealized losses | 59 |
State of Michigan and all its political subdivisions [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized cost of securities | 18,200,000 | 23,400,000
Available for sale securities/Fair Value | 18,600,000 | 24,600,000
U.S. Government agency debt obligations and mortgage-backed securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Carrying value of securities pledged to secure repurchase agreements | $ 85,200,000 | $ 83,800,000

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- Definition This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + 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=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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