Available-For-Sale And Held-To-Maturity Securities (Contractual Maturities) (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, debt maturities, within one year, Fair Value	[1]	$ 162,402
Available-for-sale Securities, debt maturities, after one year through five, Fair Value	[1]	553,787
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 one year through five, Amortized Cost		59,336
Held-to-maturity Securities, debt maturities, after five year through ten, 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
U.S. Government Agency Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, debt maturities, within one year, Fair Value	[1]	1,996
Available-for-sale Securities, debt maturities, after one year through five, Fair Value	[1]	2,690
Available-for-sale Securities, debt maturities, Fair Value	[1]	4,686
State And Municipal Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, debt maturities, within one year, Fair Value	[1]	375
Available-for-sale Securities, debt maturities, after one year through five, Fair Value	[1]	189
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	16,621
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	54,776
Available-for-sale Securities, debt maturities, Fair Value	[1]	71,961
Corporate Fixed Income Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, debt maturities, within one year, Fair Value	[1]	160,031
Available-for-sale Securities, debt maturities, after one year through five, Fair Value	[1]	550,908
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	361,437
Available-for-sale Securities, debt maturities, Fair Value	[1]	1,072,376
Held-to-maturity Securities, debt maturities, within one year, Amortized Cost		40,027
Held-to-maturity Securities, Amortized cost	[2]	40,027	40,078
Asset-Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	419,146
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	1,739,889
Available-for-sale Securities, debt maturities, Fair Value	[1]	2,159,035
Held-to-maturity Securities, debt maturities, after five year through ten, Amortized Cost		335,021
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,728,268
Held-to-maturity Securities, Amortized cost	[2]	2,063,289	1,370,300
Mortgage Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
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 five year through ten, Amortized Cost		152,555
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,239,558
Mortgage Backed Securities [Member] | Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	361
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	311,527
Available-for-sale Securities, debt maturities, Fair Value	[1]	311,888
Held-to-maturity Securities, debt maturities, after five year through ten, Amortized Cost		152,555
Held-to-maturity Securities, debt maturities, after ten years, Amortized Cost		1,239,558
Held-to-maturity Securities, Amortized cost	[2]	1,392,113	1,567,758
Mortgage Backed Securities [Member] | Commercial [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, debt maturities, after five through ten years, fair value	[1]	55,621
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	17,112
Available-for-sale Securities, debt maturities, Fair Value	[1]	72,733
Held-to-maturity Securities, debt maturities, after one year through five, Amortized Cost		59,336
Held-to-maturity Securities, Amortized cost	[2]	59,336	59,581
Mortgage Backed Securities [Member] | Non-Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Availably-for-sale Securities, debt maturities, after ten years, Fair Value	[1]	1,619
Available-for-sale Securities, debt maturities, Fair Value	[1]	$ 1,619
Held-to-maturity Securities, Amortized cost	[2]		$ 688

[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.