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, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Debt securities, Available-for-sale, Amortized cost, Total	$ 1,645,601
Debt securities, Available-for-sale, Estimated fair value, Within one year	130,962	[1],[2]
Debt securities, Available-for-sale, Estimated fair value, After five years through ten years	481,314	[1],[2]
Debt securities, Available-for-sale, Estimated fair value, After ten years	773,772	[1],[2]
Debt securities, Available-for-sale, Estimated fair value, Total	1,646,779	[1],[2]
Debt securities, Held-to-maturity, Amortized cost, After five years through ten years	59,433	[2]
Debt securities, Held-to-maturity, Amortized cost, After ten years	1,160,049	[2]
Held-to-maturity Securities, Amortized cost	1,274,765	[2]	1,312,115
Held-to-maturity securities, Estimated fair value	1,303,305		1,305,959
Excluding Mortgage Backed Securities [Member]
Debt securities, Available-for-sale, Amortized cost, Within one year	120,855
Debt securities, Available-for-sale, Amortized cost, After one year through three years	117,783
Debt securities, Available-for-sale, Amortized cost, After three years through five years	139,844
Debt securities, Available-for-sale, Amortized cost, After five years through ten years	407,502
Debt securities, Available-for-sale, Amortized cost, After ten years	459,694
Debt securities, Available-for-sale, Estimated fair value, Within one year	121,946
Debt securities, Available-for-sale, Estimated fair value, After one year through three years	119,206
Debt securities, Available-for-sale, Estimated fair value, After three years through five years	141,325
Debt securities, Available-for-sale, Estimated fair value, After five years through ten years	408,058
Debt securities, Available-for-sale, Estimated fair value, After ten years	452,765
Debt securities, Held-to-maturity, Amortized cost, Within one year
Debt securities, Held-to-maturity, Amortized cost, After one year through three years	15,038
Debt securities, Held-to-maturity, Amortized cost, After three years through five years	40,245
Debt securities, Held-to-maturity, Amortized cost, After five years through ten years
Debt securities, Held-to-maturity, Amortized cost, After ten years	228,960
Debt securities, Held-to-maturity, Estimated fair value, Within one year
Debt securities, Held-to-maturity, Estimated fair value, After one year through three years	15,041
Debt securities, Held-to-maturity, Estimated fair value, After three years through five years	38,643
Debt securities, Held-to-maturity, Estimated fair value, After five years through ten years
Debt securities, Held-to-maturity, Estimated fair value, After ten years	233,158
Mortgage-backed securities [Member]
Debt securities, Available-for-sale, Amortized cost, After one year through three years	8,951
Debt securities, Available-for-sale, Amortized cost, After three years through five years	196
Debt securities, Available-for-sale, Amortized cost, After five years through ten years	71,608
Debt securities, Available-for-sale, Amortized cost, After ten years	319,168
Debt securities, Available-for-sale, Estimated fair value, After one year through three years	9,016
Debt securities, Available-for-sale, Estimated fair value, After three years through five years	200
Debt securities, Available-for-sale, Estimated fair value, After five years through ten years	73,256
Debt securities, Available-for-sale, Estimated fair value, After ten years	321,007
Debt securities, Held-to-maturity, Amortized cost, After one year through three years
Debt securities, Held-to-maturity, Amortized cost, After three years through five years
Debt securities, Held-to-maturity, Amortized cost, After five years through ten years	59,433
Debt securities, Held-to-maturity, Amortized cost, After ten years	931,089
Debt securities, Held-to-maturity, Estimated fair value, After one year through three years
Debt securities, Held-to-maturity, Estimated fair value, After three years through five years
Debt securities, Held-to-maturity, Estimated fair value, After five years through ten years	61,605
Debt securities, Held-to-maturity, Estimated fair value, After ten years	$ 954,858

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

[2] The weighted average yield is computed using the expected maturity of each security weighted based on the amortized cost of each security.