Investment Securities (Schedule Of Maturities Of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Available-for-sale securities, due within one year, amortized cost	$ 4,845
Available-for-sale securities, after one year through five years, amortized cost	72,849
Available-for-sale securities, after five years through ten years, amortized cost	646,027
Available-for-sale securities, after ten years, amortized cost	1,962,241
Available-for-sale securities, amortized cost	2,685,962	$ 3,045,887
Available-for-sale securities, due within one year, fair value	4,884
Available-for-sale securities, after one year through five years, fair value	73,246
Available-for-sale securities, after five years through ten years, fair value	649,917
Available-for-sale securities, after ten years, fair value	1,970,351
Debt Securities, Available-for-sale	2,698,398	2,977,108
Held-to-maturity securities, due within one year, amortized cost	0
Held-to-maturity securities, after one year through five years, amortized cost	0
Held-to-maturity securities, after five years through ten years, amortized cost	18
Held-to-maturity securities, after ten years, amortized cost	3,398
Investment securities held to maturity	3,416	3,606
Held-to-maturity securities, due within one year, fair value	0
Held-to-maturity securities, after one year through five years, fair value	0
Held-to-maturity securities, after five years through ten years, fair value	18
Held-to-maturity securities, after ten years, fair value	4,444
Held-to-maturity securities, fair value	$ 4,462	$ 4,644