Investment Securities (Summary of Amortized Cost and Fair Value of Available-For-Sale Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	$ 659,183	$ 688,385	$ 697,247
Investment securities available-for-sale, Unrealized Gains	3,794	3,587	7,110
Investment securities available-for-sale, Unrealized Losses	5,159	7,402	735
Available-for-sale Securities, Total	657,818	684,570	703,622
Government sponsored agencies [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	91,613	93,895	94,939
Investment securities available-for-sale, Unrealized Gains	295	250	608
Investment securities available-for-sale, Unrealized Losses	298	382	168
Available-for-sale Securities, Total	91,610	93,763	95,379
State and political subdivisions [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	42,369	42,450	47,043
Investment securities available-for-sale, Unrealized Gains	1,408	1,355	2,206
Investment securities available-for-sale, Unrealized Losses	0	7	0
Available-for-sale Securities, Total	43,777	43,798	49,249
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	291,187	303,495	237,256
Investment securities available-for-sale, Unrealized Gains	1,023	968	1,984
Investment securities available-for-sale, Unrealized Losses	3,472	5,097	48
Available-for-sale Securities, Total	288,738	299,366	239,192
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	167,622	182,128	246,751
Investment securities available-for-sale, Unrealized Gains	393	452	1,087
Investment securities available-for-sale, Unrealized Losses	1,296	1,639	170
Available-for-sale Securities, Total	166,719	180,941	247,668
Corporate bonds [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	65,003	65,028	65,114
Investment securities available-for-sale, Unrealized Gains	505	499	783
Investment securities available-for-sale, Unrealized Losses	93	252	349
Available-for-sale Securities, Total	65,415	65,275	65,548
Preferred stock [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	1,389	1,389	6,144
Investment securities available-for-sale, Unrealized Gains	170	63	442
Investment securities available-for-sale, Unrealized Losses	0	25	0
Available-for-sale Securities, Total	$ 1,559	$ 1,427	$ 6,586