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		Mar. 31, 2017	Dec. 31, 2016
Schedule Of Debt Securities At Amortized Cost And Fair Value Basis [Line Items]
Available-for-sale Securities, debt maturities, Amortized Cost		$ 3,380,629
Available-for-sale Securities, debt maturities, within one year, Fair Value	[1]	23,852
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	773,545
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	1,896,760
Available-for-sale Securities, debt maturities, Fair Value	[1]	3,377,981
Held-to-maturity Securities, debt maturities, within one year, Amortized Cost		40,061
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		431,327
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		2,658,806
Held-to-maturity Securities, Amortized cost	[2]	3,189,767	$ 3,038,405
Held-to-maturity Securities, debt maturities, Fair Value	[2]	3,199,113	$ 3,040,554
Excluding Mortgage Backed Securities [Member]
Schedule Of Debt Securities At Amortized Cost And Fair Value Basis [Line Items]
Available-for-sale Securities, debt maturities, within one year, Amortized Cost		23,853
Available-for-sale Securities, debt maturities, after one year through three years, Amortized Cost		332,237
Available-for-sale Securities, debt maturities, after three year through five years, Amortized Cost		353,111
Available-for-sale Securities, debt maturities, after five through ten years, Amortized Cost		716,617
Availably-for-sale Securities, debt maturities, after ten years, Amortized Cost		1,533,130
Available-for-sale Securities, debt maturities, within one year, Fair Value		23,852
Available-for-sale Securities, debt maturities, after one year through three years, Fair Value		333,154
Available-for-sale Securities, debt maturities, after three year through five years, Fair Value		350,670
Available-for-sale Securities, debt maturities, after five through ten years, fair value		718,194
Availably-for-sale Securities, debt maturities, after ten years, Fair Value		1,536,568
Held-to-maturity Securities, debt maturities, within one year, Amortized Cost		40,061
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		270,998
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,309,165
Held-to-maturity Securities, debt maturities, within one year, Fair Value		40,136
Held-to-maturity Securities, debt maturities, after five through ten years, Fair Value		271,638
Held-to-maturity Securities, debt maturities, after ten years, Fair Value		1,317,385
Mortgage Backed Securities [Member]
Schedule Of Debt Securities At Amortized Cost And Fair Value Basis [Line Items]
Available-for-sale Securities, debt maturities, after five through ten years, Amortized Cost		58,788
Availably-for-sale Securities, debt maturities, after ten years, Amortized Cost		362,893
Available-for-sale Securities, debt maturities, after five through ten years, fair value		55,351
Availably-for-sale Securities, debt maturities, after ten years, Fair Value		360,192
Held-to-maturity Securities, debt maturities, after three year through five years, Amortized Cost		59,573
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		160,329
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,349,641
Held-to-maturity Securities, debt maturities, after three year through five years, Fair Value		61,152
Held-to-maturity Securities, debt maturities, after five through ten years, Fair Value		158,931
Held-to-maturity Securities, debt maturities, after ten years, Fair Value		$ 1,349,871

[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.