Loans (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 BaordOfDirectors Segment Loans Tenants	Jun. 30, 2011	Dec. 31, 2011
Loans (Additional Textual) [Abstract]
Number of portfolio segment		2
Number of classes of loans		7
Number of tenants under lease of real estate		1
Number of members of the board of directors in loan committee		10
Total nonaccrual loans	$ 33.4	$ 33.4	$ 52.0	$ 41.8
Difference between recorded investment and unpaid principal balance of loan	23.1	23.1	32.4	32.1
Confirmed losses (partial charge-offs)		19.1	22.6	21.7
Fair value of discount adjustment		4.0	9.8	10.4
Acquired impaired loans	13.6	13.6	18.6	17.4
Performing trouble debt restructuring under impaired loans	26.4	26.4	12.9	20.4
Financing receivable allowance for acquired loans	2.2	2.2		1.6
Number of minimum days for performing and nonperforming trouble debt restructuring	90 days	90 days
Commercial Loan Portfolio [Member]
Loans (Textual) [Abstract]
Minimum value of loan requires executive and senior officer approval	1.5	1.5
Minimum value of loan requires loans risk rating and credit action approval	5.0	5.0
Original contractual terms		90 days
Minimum due period of loans consider in a nonperforming status		90 days
Commercial [Member]
Loans (Textual) [Abstract]
Minimum value of loan requires group loan authority approval	1.0	1.0
Maximum value of loan requires executive and senior officer approval	3.5	3.5
Minimum value of loan requires board of director approval	10	10
Real Estate Residential Loans [Member]
Loans (Textual) [Abstract]
Period for loan secured under real estate residential security		15 years
Loan-to-value ratio at the time of origination		80.00%
Land Development Loans [Member]
Loans (Textual) [Abstract]
Maximum period for payment of loan		12 months
Maximum [Member]
Loans (Textual) [Abstract]
Upper limit of number of family residential properties		4
Maximum [Member] | Commercial Loan Portfolio [Member]
Loans (Textual) [Abstract]
Maximum value of loan requires group loan authority approval	5.0	5.0
Maximum [Member] | Commercial [Member]
Loans (Textual) [Abstract]
Maximum value of loan requires director loan committee approval	10.0	10.0
Minimum [Member]
Loans (Textual) [Abstract]
Lower limit of number of family residential properties		1
Minimum [Member] | Commercial Loan Portfolio [Member]
Loans (Textual) [Abstract]
Minimum value of loan requires group loan authority approval	1.0	1.0
Minimum [Member] | Commercial [Member]
Loans (Textual) [Abstract]
Minimum value of loan requires director loan committee approval	$ 5.0	$ 5.0