Investment Securities (Summary of Amortized Cost and Fair Value of Available-For-Sale Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	$ 614,744	$ 688,385	$ 735,443
Investment securities available-for-sale, Unrealized Gains	4,005	3,587	4,463
Investment securities available-for-sale, Unrealized Losses	2,774	7,402	5,854
Available-for-sale Securities, Total	615,975	684,570	734,052
Government sponsored agencies [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	88,503	93,895	92,239
Investment securities available-for-sale, Unrealized Gains	346	250	249
Investment securities available-for-sale, Unrealized Losses	141	382	400
Available-for-sale Securities, Total	88,708	93,763	92,088
State and political subdivisions [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	40,165	42,450	44,288
Investment securities available-for-sale, Unrealized Gains	1,443	1,355	1,500
Investment securities available-for-sale, Unrealized Losses	0	7	8
Available-for-sale Securities, Total	41,608	43,798	45,780
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	265,673	303,495	311,425
Investment securities available-for-sale, Unrealized Gains	1,117	968	1,166
Investment securities available-for-sale, Unrealized Losses	1,422	5,097	4,219
Available-for-sale Securities, Total	265,368	299,366	308,372
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	154,035	182,128	221,025
Investment securities available-for-sale, Unrealized Gains	376	452	463
Investment securities available-for-sale, Unrealized Losses	1,128	1,639	973
Available-for-sale Securities, Total	153,283	180,941	220,515
Corporate bonds [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	64,979	65,028	65,077
Investment securities available-for-sale, Unrealized Gains	456	499	692
Investment securities available-for-sale, Unrealized Losses	83	252	254
Available-for-sale Securities, Total	65,352	65,275	65,515
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	267	63	393
Investment securities available-for-sale, Unrealized Losses	0	25	0
Available-for-sale Securities, Total	$ 1,656	$ 1,427	$ 1,782