Investment Securities (Schedule Of Maturities Of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Available-for-sale securities, three months or less, amortized cost	$ 722
Available-for-sale securities, over three months through twelve months, amortized cost	1,272
Available-for-sale securities, after one year through five years, amortized cost	58,973
Available-for-sale securities, after five years through ten years, amortized cost	406,007
Available-for-sale securities, after ten years, amortized cost	2,680,038
Available-for-sale securities, amortized cost	3,148,971
Available-for-sale securities, three months or less, fair value	724
Available-for-sale securities, over three months through twelve months, fair value	1,281
Available-for-sale securities, after one year through five years, fair value	59,861
Available-for-sale securities, after five years through ten years, fair value	409,846
Available-for-sale securities, after ten years, fair value	2,658,873
Available-for-sale securities, fair value	3,132,566
Held-to-maturity securities, three months or less, amortized cost	0
Held-to-maturity securities, over three months through twelve months, 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	19
Held-to-maturity securities, after ten years, amortized cost	3,998
Investment securities held to maturity	4,017	$ 4,216
Held-to-maturity securities, three months or less, fair value	0
Held-to-maturity securities, over three months through twelve months, 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	20
Held-to-maturity securities, after ten years, fair value	5,051
Held-to-maturity securities, fair value	5,071	$ 5,217
Other Investment Securities
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	1,959
Available-for-sale securities, fair value	1,981
Investment securities held to maturity	0
Held-to-maturity securities, fair value	$ 0