Investment Securities (Schedule Of Contractual Maturities Of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Available-for-sale securities, due within one year, amortized cost	$ 21,169
Available-for-sale securities, after one year through five years, amortized cost	90,837
Available-for-sale securities, after five years through ten years, amortized cost	398,942
Available-for-sale securities, after ten years, amortized cost	2,534,939
Available-for-sale securities, amortized cost	3,045,887	$ 3,099,329
Available-for-sale securities, due within one year, fair value	21,140
Available-for-sale securities, after one year through five years, fair value	90,367
Available-for-sale securities, after five years through ten years, fair value	393,068
Available-for-sale securities, after ten years, fair value	2,472,533
Available-for-sale securities, fair value	2,977,108	3,065,769
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	15
Held-to-maturity securities, after ten years, amortized cost	3,591
Held to maturity, at amortized cost	3,606	3,803
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	15
Held-to-maturity securities, after ten years, fair value	4,629
Held-to-maturity securities, fair value	$ 4,644	$ 4,906