Securities (Additional Information) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
security
Dec. 31, 2013
security
Dec. 31, 2012
security
Schedule of Investments [Line Items]      
Unrealized gains on securities available-for-sale included in accumulated other comprehensive income, net of deferred taxes $ (319,000) $ (7,964,000)  
Unrealized gains on securities available-for-sale included in accumulated other comprehensive income, deferred taxes 172,000 4,288,000  
Number of investment securities which had unrealized losses for twelve months or longer 74 93  
AFS and HTM securities in Continues Unrealized Loss Position 434,100,000 509,200,000  
AFS and HTM Securities Unrealized Loss Accumulated in Investments 7,900,000 19,800,000  
Investment securities with unrealized losses for twelve months or longer 307,951,000 122,236,000  
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 7,313,000 7,834,000  
Investment securities with unrealized losses that are considered temporary 428,315,000 509,203,000  
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments (7,924,000) (19,776,000)  
Other than temporary impairment losses 0 0  
Carrying value of investments sold 25,200,000 16,800,000 113,000,000
Security pledged as collateral, amortized cost 486,200,000 479,200,000  
Security pledged as collateral, fair value 485,600,000 474,700,000  
Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]      
Schedule of Investments [Line Items]      
Investment securities with unrealized losses for twelve months or longer 308,000,000 117,300,000  
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 7,300,000 7,400,000  
Private issue collateralized mortgage obligations [Member]      
Schedule of Investments [Line Items]      
Investment securities with unrealized losses for twelve months or longer 0 4,945,000  
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 0 403,000  
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year 0    
Investment securities with unrealized losses that are considered temporary 1,785,000 5,067,000  
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments (8,000) (407,000)  
Other Than Temporary Impairment, Number of Securities     1
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold     $ 176,000