Securities (Amortized Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale, Amortized Cost
Due in one year or less	$ 2,381
Due after one year through five years	97,183
Due after five years through ten years	96,658
Due after ten years	567,331
Total	763,553
Available-for-sale, Fair Value
Due in one year or less	2,416
Due after one year through five years	97,441
Due after five years through ten years	98,023
Due after ten years	565,183
Total	763,063
Held-to-maturity, Amortized Cost
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	2,316
Due after ten years	17,863
Held-to-maturity Securities	20,179	0
Held-to-maturity, Fair Value
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	2,330
Due after ten years	18,095
Held-to-maturity Securities, Fair Value	$ 20,425