Securities (Summary of Amortized Costs and Estimated Fair Values of Available-For-Sale Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	$ 763,553	$ 820,728
Available-for-sale, Unrealized Gains	7,434	7,525
Available-for-sale, Unrealized Losses	(7,924)	(19,776)
AFS securities	763,063us-gaap_AvailableForSaleSecurities	808,477us-gaap_AvailableForSaleSecurities
Held-to-maturity Securities	20,179us-gaap_HeldToMaturitySecurities	0us-gaap_HeldToMaturitySecurities
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	265
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(19)
Held-to-maturity Securities, Fair Value	20,425
US Government Corporations and Agencies Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	4,962
Available-for-sale, Unrealized Gains	65
Available-for-sale, Unrealized Losses	0
AFS securities	5,027
Held-to-maturity Securities	20,179
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	265
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(19)
Held-to-maturity Securities, Fair Value	20,425
Obligations of states and political subdivisions [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	26,080	30,143
Available-for-sale, Unrealized Gains	697	1,075
Available-for-sale, Unrealized Losses	0	(11)
AFS securities	26,777	31,207
Mortgage-backed securities issued or guaranteed by U.S. government sponsored enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	377,657	397,409
Available-for-sale, Unrealized Gains	5,656	5,528
Available-for-sale, Unrealized Losses	(2,005)	(7,034)
AFS securities	381,308	395,903
Collateralized mortgage obligations issued or guaranteed by U.S. government sponsored enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	348,855	385,847
Available-for-sale, Unrealized Gains	953	912
Available-for-sale, Unrealized Losses	(5,911)	(12,324)
AFS securities	343,897	374,435
Private issue collateralized mortgage obligations [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	5,999	7,329
Available-for-sale, Unrealized Gains	63	10
Available-for-sale, Unrealized Losses	(8)	(407)
AFS securities	$ 6,054	$ 6,932

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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