Investment Securities (Summary of the Amortized Cost and Fair Value of Investment Securities by Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investment Securities Available-for-Sale: Amortized Cost
Due in one year or less	$ 237,047
Due after one year through five years	490,634
Due after five years through ten years	339,222
Due after ten years	188,429
Preferred stock	1,389
Total	1,256,721
Investment Securities Available-for-Sale: Fair Value
Due in one year or less	235,845
Due after one year through five years	485,221
Due after five years through ten years	329,879
Due after ten years	182,281
Preferred stock	1,738
Total	1,234,964
Investment Securities Held-to-Maturity: Amortized Cost
Due in one year or less	66,090
Due after one year through five years	262,136
Due after five years through ten years	145,225
Due after ten years	149,976
Total	623,427	$ 509,971
Investment Securities Held-to-Maturity: Fair Value
Due in one year or less	65,954
Due after one year through five years	257,936
Due after five years through ten years	139,320
Due after ten years	145,321
Total	$ 608,531	$ 512,705