Investment Securities (Summary of the Amortized Cost and Fair Value of Investment Securities by Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investment Securities Available-for-Sale:
Due in one year or less, Amortized Cost	$ 144,423
Due after one year through five years, Amortized Cost	436,081
Due after five years through ten years, Amortized Cost	101,624
Due after ten years, Amortized Cost	4,868
Preferred stock, Amortized Cost	1,389
Total Available-for-sale Securities, Amortized Cost	688,385
Due in one year or less , Fair Value	143,762
Due after one year through five years, Fair Value	434,027
Due after five years through ten years, Fair Value	100,642
Due after ten years, Fair Value	4,712
Preferred stock, Fair Value	1,427
Total Available-for-sale securities, Fair Value	684,570
Investment Securities Held-to-Maturity:
Due in one year or less, Amortized Cost	39,966
Due after one year through five years, Amortized Cost	106,380
Due after five years through ten years, Amortized Cost	74,759
Due after ten years, Amortized Cost	52,800
Total Held-to-maturity securities, Amortized Cost	273,905	229,977
Due in one year or less , Fair Value	39,981
Due after one year through five years, Fair Value	107,688
Due after five years through ten years, Fair Value	75,563
Due after ten years, Fair Value	45,039
Total Held-to-maturity securities, Fair Value	$ 268,271	$ 229,922