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		Jun. 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		$ 3,451,901
Available-for-sale Securities, debt maturities, within one year, Fair Value	[1]	142,514
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	759,825
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	1,981,696
Available-for-sale Securities, debt maturities, Fair Value	[1]	3,455,373
Held-to-maturity Securities, debt maturities, within one year, Amortized Cost		40,045
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		497,440
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		2,710,967
Held-to-maturity Securities, Amortized cost	[2]	3,307,970	$ 3,038,405
Held-to-maturity Securities, debt maturities, Fair Value	[2]	3,321,880	$ 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		142,136
Available-for-sale Securities, debt maturities, after one year through three years, Amortized Cost		138,597
Available-for-sale Securities, debt maturities, after three year through five years, Amortized Cost		432,593
Available-for-sale Securities, debt maturities, after five through ten years, Amortized Cost		702,630
Availably-for-sale Securities, debt maturities, after ten years, Amortized Cost		1,636,741
Available-for-sale Securities, debt maturities, within one year, Fair Value		142,514
Available-for-sale Securities, debt maturities, after one year through three years, Fair Value		139,032
Available-for-sale Securities, debt maturities, after three year through five years, Fair Value		432,306
Available-for-sale Securities, debt maturities, after five through ten years, fair value		703,979
Availably-for-sale Securities, debt maturities, after ten years, Fair Value		1,644,175
Held-to-maturity Securities, debt maturities, within one year, Amortized Cost		40,045
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		335,011
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,419,082
Held-to-maturity Securities, debt maturities, within one year, Fair Value		40,114
Held-to-maturity Securities, debt maturities, after five through ten years, Fair Value		335,513
Held-to-maturity Securities, debt maturities, after ten years, Fair Value		1,427,922
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		58,618
Availably-for-sale Securities, debt maturities, after ten years, Amortized Cost		340,586
Available-for-sale Securities, debt maturities, after five through ten years, fair value		55,846
Availably-for-sale Securities, debt maturities, after ten years, Fair Value		337,521
Held-to-maturity Securities, debt maturities, after three year through five years, Amortized Cost		59,518
Held-to-maturity Securities, debt maturities, after five through ten years, Amortized Cost		162,429
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,291,885
Held-to-maturity Securities, debt maturities, after three year through five years, Fair Value		61,606
Held-to-maturity Securities, debt maturities, after five through ten years, Fair Value		161,038
Held-to-maturity Securities, debt maturities, after ten years, Fair Value		$ 1,295,687

[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.