Investment Securities (Maturities of Debt Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Investment Securities Available-for-Sale:
Due in one year or less, Amortized Cost	$ 154,820
Due after one year through five years, Amortized Cost	257,040
Due after five years through ten years, Amortized Cost	37,877
Due after ten years, Amortized Cost	4,049
Preferred stock, Amortized Cost	1,388
Total Available-for-sale Securities, Debt Maturities, Amortized Cost	455,174
Due in one year or less , Fair Value	155,386
Due after one year through five years, Fair Value	258,856
Due after five years through ten years, Fair Value	38,374
Due after ten years, Fair Value	4,112
Preferred stock, Fair Value	1,824
Total Available-for-sale securities, Debt maturities, Fair Value	458,552
Investment Securities Held-to-Maturity:
Due in one year or less, Amortized Cost	59,330
Due after one year through five years, Amortized Cost	275,988
Due after five years through ten years, Amortized Cost	130,304
Due after ten years, Amortized Cost	87,206
Total Held-to-maturity securities, Debt maturities, Amortized Cost	552,828	$ 509,971	$ 469,837
Due in one year or less , Fair Value	59,633
Due after one year through five years, Fair Value	280,491
Due after five years through ten years, Fair Value	136,879
Due after ten years, Fair Value	91,412
Total Held-to-maturity securities, Debt maturities, Fair Value	$ 568,415	$ 512,705	$ 466,578