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Hedging Activities (Details) (USD $) | 1 Months Ended | 3 Months Ended |  |  | 1 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 30, 2011 BasisPoints | Mar. 31, 2013 | Dec. 31, 2012 | Feb. 29, 2012 | Feb. 29, 2012 Interest rate swap agreement [Member] BasisPoints | Jun. 30, 2011 Interest rate cap contracts [Member] | Mar. 31, 2013 Mercantile Bank Prime Rate [Member] | Mar. 31, 2013 Wall Street Journal Prime Rate [Member] | Dec. 31, 2008 Wall Street Journal Prime Rate [Member] | Oct. 31, 2008 Wall Street Journal Prime Rate [Member]
Hedging Activities (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |
Prime Rate Percentage |  |  |  |  |  |  | 4.50% | 3.25% |  |
Decline in Prime Rate |  |  |  |  |  |  |  |  | 0.75% | 0.50%
Notional amount of purchased interest rate cap |  | $ 18,800,000 |  |  |  | $ 100,000,000 |  |  |  |
Rate used to determine payment received from correspondent bank on notional amount of interest rate swap/Basis for determining strike rate on purchased interest rate cap | 30-Day Libor Rate |  |  |  | 90-Day Libor Rate |  |  |  |  |
Trust preferred securities interest rate index |  |  |  |  | 90-Day Libor Rate |  |  |  |  |
Fixed spread added to the variable rate on our trust preferred securities |  |  |  |  | 218 |  |  |  |  |
Notional amount of interest rate swap |  |  |  |  | 32,000,000 |  |  |  |  |
Hedging Activities (Additional Textual) [Abstract] |  |  |  |  |  |  |  |  |  |
Variable commercial loans as a percentage of total assets |  | 38.00% |  |  |  |  |  |  |  |
Strike rate of sold interest rate cap in basis points above strike rate on purchased interest rate cap | 125 |  |  |  |  |  |  |  |  |
Notional amount of sold interest rate cap | 100,000,000 |  |  |  |  |  |  |  |  |
Payment made under interest rate cap contract |  | 0 |  |  |  |  |  |  |  |
Subordinated debentures |  |  |  | 32,000,000 |  |  |  |  |  |
Interest rate swap agreement effective date |  | 2013-01 |  |  |  |  |  |  |  |
Interest rate swap agreement maturity date |  | 2018-01 |  |  |  |  |  |  |  |
Present value of Interest rate swap, record as liability |  | $ 1,000,000 | $ 1,100,000 |  |  |  |  |  |  |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Basis point, current. + References No definition available. + Details
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- Definition Decline in prime rate. + References No definition available. + Details
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- Definition Fair value of interest rate swap agreement liability. + References No definition available. + Details
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- Definition Fixed spread added to the variable rate on our trust preferred securities. + References No definition available. + Details
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- Details
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- Definition Hedging activities interest rate swap agreement effective date. + References No definition available. + Details
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- Details
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- Definition The reference rate for the variable rate of the interest rate derivative, 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
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- Definition Aggregate notional amount of interest rate derivatives, which relates to the currency amount specified in the interest rate derivative instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Notional Amount -URI http://asc.fasb.org/extlink&oid=6519104 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959 + Details
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- Definition Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section F Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Article 5 -Subsection 19, 20, 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 + Details
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