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, 2012
Debt securities, Available-for-sale, Amortized cost, Within one year	$ 36,257
Debt securities, Available-for-sale, Amortized cost, After one year through three years	318,885
Debt securities, Available-for-sale, Amortized cost, After three years through five years	118,776
Debt securities, Available-for-sale, Amortized cost, After five years through ten years	5,583
Debt securities, Available-for-sale, Amortized cost, After ten years	92,438
Debt securities, Available-for-sale, Amortized cost, Total	1,329,751
Debt securities, Available-for-sale, Estimated fair value, Within one year	36,424
Debt securities, Available-for-sale, Estimated fair value, After one year through three years	322,515
Debt securities, Available-for-sale, Estimated fair value, After three years through five years	116,776
Debt securities, Available-for-sale, Estimated fair value, After five years through ten years	6,207
Debt securities, Available-for-sale, Estimated fair value, After ten years	96,174
Debt securities, Available-for-sale, Estimated fair value, Total	1,347,535
Debt securities, Held-to-maturity, Amortized cost, After three years through five years	21,265
Debt securities, Held-to-maturity, Amortized cost, After five years through ten years	143,413
Debt securities, Held-to-maturity, Amortized cost, After ten years	162,769
Debt securities, Held-to-maturity, Amortized cost, Total	327,447
Debt securities, Held-to-maturity, Estimated fair value, After three years through five years	20,909
Debt securities, Held-to-maturity, Estimated fair value, After five years through ten years	142,717
Debt securities, Held-to-maturity, Estimated fair value, After ten years	166,207
Debt securities, Held-to-maturity, Estimated fair value, Total	329,833
Mortgage-backed securities [Member]
Debt securities, Available-for-sale, Amortized cost, After one year through three years	9,528
Debt securities, Available-for-sale, Amortized cost, After five years through ten years	17,408
Debt securities, Available-for-sale, Amortized cost, After ten years	730,876
Debt securities, Available-for-sale, Estimated fair value, After one year through three years	10,003
Debt securities, Available-for-sale, Estimated fair value, After five years through ten years	17,815
Debt securities, Available-for-sale, Estimated fair value, After ten years	$ 741,621