Investment Securities (Schedule Of Maturities Of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Available-for-sale securities, due within one year, amortized cost	$ 21,769
Available-for-sale securities, after one year through five years, amortized cost	74,546
Available-for-sale securities, after five years through ten years, amortized cost	864,633
Available-for-sale securities, after ten years, amortized cost	1,768,167
Available-for-sale securities, amortized cost	2,729,115	$ 2,790,248
Available-for-sale securities, due within one year, fair value	21,844
Available-for-sale securities, after one year through five years, fair value	76,542
Available-for-sale securities, after five years through ten years, fair value	932,715
Available-for-sale securities, after ten years, fair value	1,834,589
Debt Securities, Available-for-sale	2,865,690	2,814,682
Held-to-maturity securities, due within one year, amortized cost	0
Held-to-maturity securities, after one year through five years, amortized cost	3
Held-to-maturity securities, after five years through ten years, amortized cost	11
Held-to-maturity securities, after ten years, amortized cost	3,129
Investment securities held to maturity	3,143	3,260
Held-to-maturity securities, due within one year, fair value	0
Held-to-maturity securities, after one year through five years, fair value	3
Held-to-maturity securities, after five years through ten years, fair value	11
Held-to-maturity securities, after ten years, fair value	3,955
Held-to-maturity securities, fair value	$ 3,969	$ 4,263