Securities (Details Textual) (USD $)	12 Months Ended
	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