Investment Securities (Summary of Amortized Cost and Fair Value of Available-For-Sale Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	$ 707,655	$ 580,234	$ 639,315
Investment securities available-for-sale, Unrealized Gains	3,784	7,518	8,448
Investment securities available-for-sale, Unrealized Losses	6,293	943	1,185
Available-for-sale Securities, Total	705,146	586,809	646,578
Government sponsored agencies [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	86,065	97,529	101,576
Investment securities available-for-sale, Unrealized Gains	264	241	182
Investment securities available-for-sale, Unrealized Losses	404	213	266
Available-for-sale Securities, Total	85,925	97,557	101,492
State and political subdivisions [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	44,191	47,663	49,707
Investment securities available-for-sale, Unrealized Gains	1,386	2,302	2,538
Investment securities available-for-sale, Unrealized Losses	5	0	7
Available-for-sale Securities, Total	45,572	49,965	52,238
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	310,550	96,320	101,709
Investment securities available-for-sale, Unrealized Gains	1,144	3,100	3,543
Investment securities available-for-sale, Unrealized Losses	3,534	9	16
Available-for-sale Securities, Total	308,160	99,411	105,236
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	200,407	262,790	297,960
Investment securities available-for-sale, Unrealized Gains	199	984	1,392
Investment securities available-for-sale, Unrealized Losses	2,148	182	274
Available-for-sale Securities, Total	198,458	263,592	299,078
Corporate bonds [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	65,053	69,788	82,219
Investment securities available-for-sale, Unrealized Gains	583	546	509
Investment securities available-for-sale, Unrealized Losses	202	539	622
Available-for-sale Securities, Total	65,434	69,795	82,106
Preferred stock [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	1,389	6,144	6,144
Investment securities available-for-sale, Unrealized Gains	208	345	284
Investment securities available-for-sale, Unrealized Losses	0	0	0
Available-for-sale Securities, Total	$ 1,597	$ 6,489	$ 6,428