Loans (Textual) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) Segment Loans BaordOfDirectors Tenants	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)
Loans (Textual) [Abstract]
Number of portfolio segment | Segment	2
Number of classes of loans | Loans	6
Number of minimum tenants under lease of non-owner occupied commercial real estate | Tenants	1
Number of members of the board of directors in loan committee | BaordOfDirectors	8
Minimum due period of loans consider in a nonperforming status	90 days
Total nonaccrual TDR loans	$ 32.5	$ 35.9	$ 37.3
Residential Mortgage Loans in Process of Foreclosure	2.3	2.9	2.2
Difference between recorded investment and unpaid principal balance of loan	25.9	25.3	29.7
Confirmed losses (partial charge-offs)	19.9	17.1	14.8
Fair value of discount adjustment	6.0	8.2	14.9
Acquired impaired loans	10.1	12.8	11.2
Performing trouble debt restructuring under impaired loans	49.9	$ 47.8	$ 46.0
Commercial Loan Portfolio [Member]
Loans (Textual) [Abstract]
Minimum value of loan requires executive and senior officer approval	$ 1.5
Consumer Portfolio Segment [Member]
Loans (Textual) [Abstract]
Maximum due period of loans consider in performing status	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
Maximum value of loan requires executive and senior officer approval	$ 3.5
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] | Commercial Loan Portfolio [Member]
Loans (Textual) [Abstract]
Maximum value of loan requires group loan authority approval	$ 10.0
Other loans requiring director loan committee approval depending on risk rating and credit action required	$ 10.0
Maximum [Member] | Real Estate Residential Loans [Member]
Loans (Textual) [Abstract]
Upper limit of number of family residential properties | Tenants	4
Minimum [Member] | Commercial Loan Portfolio [Member]
Loans (Textual) [Abstract]
Minimum value of loan requires group loan authority approval	$ 1.0
Minimum value of loans depending on risk rating and requires credit action from board of directors	15.0
Minimum [Member] | Commercial [Member]
Loans (Textual) [Abstract]
Minimum value of loans requiring only director loan committee approval	$ 10.0
Minimum [Member] | Real Estate Residential Loans [Member]
Loans (Textual) [Abstract]
Lower limit of number of family residential properties | Tenants	1