Investment Securities (Summary of the Amortized Cost and Fair Value of Investment Securities by Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investment Securities Available-for-Sale:
Due in one year or less, Amortized Cost	$ 170,838
Due after one year through five years, Amortized Cost	326,018
Due after five years through ten years, Amortized Cost	53,317
Due after ten years, Amortized Cost	5,074
Preferred stock, Amortized Cost	1,389
Total Available-for-sale Securities, Amortized Cost	556,636
Due in one year or less , Fair Value	170,098
Due after one year through five years, Fair Value	324,187
Due after five years through ten years, Fair Value	52,649
Due after ten years, Fair Value	5,064
Preferred stock, Fair Value	1,733
Total Available-for-sale securities, Fair Value	553,731
Investment Securities Held-to-Maturity:
Due in one year or less, Amortized Cost	59,834
Due after one year through five years, Amortized Cost	236,141
Due after five years through ten years, Amortized Cost	136,383
Due after ten years, Amortized Cost	77,613
Total Held-to-maturity securities, Amortized Cost	509,971	$ 316,413
Due in one year or less , Fair Value	59,938
Due after one year through five years, Fair Value	236,491
Due after five years through ten years, Fair Value	137,188
Due after ten years, Fair Value	79,088
Total Held-to-maturity securities, Fair Value	$ 512,705	$ 315,740