Investment Securities (Schedule Of Contractual Maturities Of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Available-for-sale securities, due within one year, amortized cost	$ 10,037
Available-for-sale securities, after one year through five years, amortized cost	106,685
Available-for-sale securities, after five years through ten years, amortized cost	884,024
Available-for-sale securities, after ten years, amortized cost	2,406,674
Available-for-sale securities, amortized cost	3,407,420	$ 2,801,500
Available-for-sale securities, due within one year, fair value	10,095
Available-for-sale securities, after one year through five years, fair value	111,680
Available-for-sale securities, after five years through ten years, fair value	930,794
Available-for-sale securities, after ten years, fair value	2,421,381
Debt Securities, Available-for-sale	3,473,950	2,932,558
Held-to-maturity securities, due within one year, amortized cost	0
Held-to-maturity securities, after one year through five years, amortized cost	2
Held-to-maturity securities, after five years through ten years, amortized cost	8
Held-to-maturity securities, after ten years, amortized cost	2,866
Investment securities held to maturity	2,876	3,034
Held-to-maturity securities, due within one year, fair value	0
Held-to-maturity securities, after one year through five years, fair value	2
Held-to-maturity securities, after five years through ten years, fair value	8
Held-to-maturity securities, after ten years, fair value	3,680
Held-to-maturity securities, fair value	$ 3,690	$ 3,883