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		Sep. 30, 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		$ 3,683,091
Available-for-sale Securities, debt maturities, within one year, Fair Value	[1]	162,402
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	853,186
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	2,124,923
Available-for-sale Securities, debt maturities, Fair Value	[1]	3,694,298
Held-to-maturity Securities, debt maturities, within one year, Amortized Cost		40,027
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		487,576
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		2,967,826
Held-to-maturity Securities, Amortized cost	[2]	3,554,765	$ 3,038,405
Held-to-maturity Securities, debt maturities, Fair Value	[2]	3,572,646	$ 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		162,117
Available-for-sale Securities, debt maturities, after one year through three years, Amortized Cost		203,072
Available-for-sale Securities, debt maturities, after three year through five years, Amortized Cost		349,602
Available-for-sale Securities, debt maturities, after five through ten years, Amortized Cost		794,146
Availably-for-sale Securities, debt maturities, after ten years, Amortized Cost		1,782,438
Available-for-sale Securities, debt maturities, within one year, Fair Value		162,402
Available-for-sale Securities, debt maturities, after one year through three years, Fair Value		204,360
Available-for-sale Securities, debt maturities, after three year through five years, Fair Value		349,427
Available-for-sale Securities, debt maturities, after five through ten years, fair value		797,204
Availably-for-sale Securities, debt maturities, after ten years, Fair Value		1,794,665
Held-to-maturity Securities, debt maturities, within one year, Amortized Cost		40,027
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		335,021
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,728,268
Held-to-maturity Securities, debt maturities, within one year, Fair Value		40,041
Held-to-maturity Securities, debt maturities, after five through ten years, Fair Value		335,834
Held-to-maturity Securities, debt maturities, after ten years, Fair Value		1,738,733
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		58,428
Availably-for-sale Securities, debt maturities, after ten years, Amortized Cost		333,288
Available-for-sale Securities, debt maturities, after five through ten years, fair value		55,982
Availably-for-sale Securities, debt maturities, after ten years, Fair Value		330,258
Held-to-maturity Securities, debt maturities, after three year through five years, Amortized Cost		59,336
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		152,555
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,239,558
Held-to-maturity Securities, debt maturities, after three year through five years, Fair Value		61,428
Held-to-maturity Securities, debt maturities, after five through ten years, Fair Value		151,316
Held-to-maturity Securities, debt maturities, after ten years, Fair Value		$ 1,245,294

[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.