Investment Securities (Summary of Amortized Cost and Fair Value of Available-For-Sale Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	$ 576,740	$ 688,385	$ 707,655
Investment securities available-for-sale, Unrealized Gains	3,469	3,587	3,784
Investment securities available-for-sale, Unrealized Losses	3,998	7,402	6,293
Available-for-sale Securities, Total	576,211	684,570	705,146
Government sponsored agencies [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	76,626	93,895	86,065
Investment securities available-for-sale, Unrealized Gains	354	250	264
Investment securities available-for-sale, Unrealized Losses	42	382	404
Available-for-sale Securities, Total	76,938	93,763	85,925
State and political subdivisions [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	39,589	42,450	44,191
Investment securities available-for-sale, Unrealized Gains	1,375	1,355	1,386
Investment securities available-for-sale, Unrealized Losses	0	7	5
Available-for-sale Securities, Total	40,964	43,798	45,572
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	252,908	303,495	310,550
Investment securities available-for-sale, Unrealized Gains	846	968	1,144
Investment securities available-for-sale, Unrealized Losses	2,715	5,097	3,534
Available-for-sale Securities, Total	251,039	299,366	308,160
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	141,273	182,128	200,407
Investment securities available-for-sale, Unrealized Gains	346	452	199
Investment securities available-for-sale, Unrealized Losses	1,174	1,639	2,148
Available-for-sale Securities, Total	140,445	180,941	198,458
Corporate bonds [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	64,955	65,028	65,053
Investment securities available-for-sale, Unrealized Gains	295	499	583
Investment securities available-for-sale, Unrealized Losses	67	252	202
Available-for-sale Securities, Total	65,183	65,275	65,434
Preferred stock [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	1,389	1,389	1,389
Investment securities available-for-sale, Unrealized Gains	253	63	208
Investment securities available-for-sale, Unrealized Losses	0	25	0
Available-for-sale Securities, Total	$ 1,642	$ 1,427	$ 1,597