Investment Securities (Amortized Cost And Fair Value Of Investment Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale, Amortized cost [Abstract]
Due before one year	$ 6,829
Due after one year through five years	100,793
Due after five years through ten years	234,846
Due after ten years	1,000,399
Total	1,342,867
Available-for-sale, Fair value [Abstract]
Due before one year	6,818
Due after one year through five years	104,670
Due after five years through ten years	242,311
Due after ten years	999,479
Fair value	1,353,278	$ 1,320,692
Held-to-maturity, Amortized cost [Abstract]
Due before one year
Due after one year through five years
Due after five years through ten years
Due after ten years
Held-to-maturity Securities, Total		84,387
Held-to-maturity, Fair value [Abstract]
Due before one year
Due after one year through five years
Due after five years through ten years
Due after ten years
Fair value		$ 83,002