Investment Securities (Summary of Amortized Cost and Fair Value of Available-For-Sale Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	$ 634,199	$ 749,187	$ 576,740
Investment securities available-for-sale, Unrealized Gains	2,908	3,003	3,469
Investment securities available-for-sale, Unrealized Losses	1,466	3,326	3,998
Available-for-sale Securities, Total	635,641	748,864	576,211
US Treasury Securities [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	6,770	8,272
Investment securities available-for-sale, Unrealized Gains	34	0
Investment securities available-for-sale, Unrealized Losses	0	13
Available-for-sale Securities, Total	6,804	8,259
Government sponsored agencies [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	208,626	263,658	76,626
Investment securities available-for-sale, Unrealized Gains	734	356	354
Investment securities available-for-sale, Unrealized Losses	480	511	42
Available-for-sale Securities, Total	208,880	263,503	76,938
State and political subdivisions [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	25,573	45,157	39,589
Investment securities available-for-sale, Unrealized Gains	465	1,087	1,375
Investment securities available-for-sale, Unrealized Losses	0	17	0
Available-for-sale Securities, Total	26,038	46,227	40,964
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	201,068	240,465	252,908
Investment securities available-for-sale, Unrealized Gains	944	885	846
Investment securities available-for-sale, Unrealized Losses	347	1,543	2,715
Available-for-sale Securities, Total	201,665	239,807	251,039
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	149,549	145,316	141,273
Investment securities available-for-sale, Unrealized Gains	398	261	346
Investment securities available-for-sale, Unrealized Losses	570	1,194	1,174
Available-for-sale Securities, Total	149,377	144,383	140,445
Corporate bonds [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	39,724	44,930	64,955
Investment securities available-for-sale, Unrealized Gains	68	213	295
Investment securities available-for-sale, Unrealized Losses	69	48	67
Available-for-sale Securities, Total	39,723	45,095	65,183
Preferred stock [Member]
Available-for-sale Securities
Investment securities available-for-sale, Amortized Cost	2,889	1,389	1,389
Investment securities available-for-sale, Unrealized Gains	265	201	253
Investment securities available-for-sale, Unrealized Losses	0	0	0
Available-for-sale Securities, Total	$ 3,154	$ 1,590	$ 1,642