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