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	Mar. 31, 2013
Debt securities, Available-for-sale, Amortized cost, Within one year	$ 130,020
Debt securities, Available-for-sale, Amortized cost, After one year through three years	290,906
Debt securities, Available-for-sale, Amortized cost, After three years through five years	31,259
Debt securities, Available-for-sale, Amortized cost, After five years through ten years	53,451
Debt securities, Available-for-sale, Amortized cost, After ten years	234,802
Debt securities, Available-for-sale, Amortized cost, Total	1,713,187
Debt securities, Available-for-sale, Estimated fair value, Within one year	130,899
Debt securities, Available-for-sale, Estimated fair value, After one year through three years	296,597
Debt securities, Available-for-sale, Estimated fair value, After three years through five years	31,718
Debt securities, Available-for-sale, Estimated fair value, After five years through ten years	53,480
Debt securities, Available-for-sale, Estimated fair value, After ten years	236,073
Debt securities, Available-for-sale, Estimated fair value, Total	1,729,837
Debt securities, Held-to-maturity, Amortized cost, Within one year
Debt securities, Held-to-maturity, Amortized cost, After one year through three years	16,154
Debt securities, Held-to-maturity, Amortized cost, After three years through five years	46,934
Debt securities, Held-to-maturity, Amortized cost, After five years through ten years	251,641
Debt securities, Held-to-maturity, Amortized cost, After ten years	401,544
Debt securities, Held-to-maturity, Amortized cost, Total	716,273
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	16,251
Debt securities, Held-to-maturity, Estimated fair value, After three years through five years	46,775
Debt securities, Held-to-maturity, Estimated fair value, After five years through ten years	253,556
Debt securities, Held-to-maturity, Estimated fair value, After ten years	409,261
Debt securities, Held-to-maturity, Estimated fair value, Total	725,843
Mortgage-backed securities [Member]
Debt securities, Available-for-sale, Amortized cost, After three years through five years	349
Debt securities, Available-for-sale, Amortized cost, After five years through ten years	16,736
Debt securities, Available-for-sale, Amortized cost, After ten years	955,664
Debt securities, Available-for-sale, Estimated fair value, After three years through five years	359
Debt securities, Available-for-sale, Estimated fair value, After five years through ten years	17,452
Debt securities, Available-for-sale, Estimated fair value, After ten years	963,259
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
Debt securities, Held-to-maturity, Amortized cost, After ten 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
Debt securities, Held-to-maturity, Estimated fair value, After ten years