Available-For-Sale And Held-To-Maturity Securities (Schedule Of Amortized Cost And Fair Values Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2019		Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Available-for-sale Securities, debt maturities, within one year, Amortized Cost	$ 6,861		$ 5,872
Available-for-sale Securities, debt maturities, after one year through three years, Amortized Cost	229,184		234,101
Available-for-sale Securities, debt maturities, after three year through five years, Amortized Cost	422,236		407,507
Available-for-sale Securities, debt maturities, after five through ten years, Amortized Cost	409,664		469,566
Available-for-sale Securities, debt maturities, after ten years, Amortized Cost	2,186,096		2,008,528
Available-for-sale Securities, debt maturities, Amortized Cost	3,254,041		3,125,574
Available-for-sale Securities, debt maturities, within one year, Fair Value	6,871	[1]	5,855
Available-for-sale Securities, debt maturities, after one year through three years, Fair Value	229,760		227,951
Available-for-sale Securities, debt maturities, after three year through five years, Fair Value	429,909		397,372
Available-for-sale Securities, debt maturities, after five through ten years, fair value	411,680	[1]	458,442
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	2,176,517	[1]	1,980,827
Available-for-sale Securities, debt maturities, Fair Value	3,254,737	[1]	3,070,447
Held-to-maturity Securities, debt maturities, after one year through three years, Amortized Cost			51,524
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost	598,250		536,717
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost	2,257,969		3,630,613
Held-to-maturity Securities, Amortized cost	2,856,219		4,218,854	[2]
Held-to-maturity Securities, debt maturities, after one year through three years, Fair Value			51,709
Held-to-maturity Securities, debt maturities, after five through ten years, Fair Value	597,166		530,616
Held-to-maturity Securities, debt maturities, after ten years, Fair Value	2,230,717		3,540,582
Held-to-maturity Securities, debt maturities, Fair Value	$ 2,827,883		$ 4,122,907	[2]

[1] Due to the immaterial amount of income recognized on tax-exempt securities, yields were not calculated on a tax-equivalent basis.

[2] Held-to-maturity securities are carried in the consolidated statements of financial condition at amortized cost, and the changes in the value of these securities, other than impairment charges, are not reported on the consolidated financial statements.