Securities (Amortized Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale, Amortized Cost
Due in one year or less	$ 2,787
Due after one year through five years	87,743
Due after five years through ten years	114,988
Due after ten years	549,956
Total	755,474
Available-for-sale, Fair Value
Due in one year or less	2,813
Due after one year through five years	87,722
Due after five years through ten years	115,359
Due after ten years	543,739
Total	749,633
Held-to-maturity, Amortized Cost
Due in one year or less	0
Due after one year through five years	2,219
Due after five years through ten years	1,125
Due after ten years	80,800
Held-to-maturity Securities	84,144	$ 20,179
Held-to-maturity, Fair Value
Due in one year or less	0
Due after one year through five years	2,269
Due after five years through ten years	1,135
Due after ten years	82,243
Held-to-maturity Securities, Fair Value	$ 85,647	$ 20,425