Investment Securities (Summary Of Debt Securities By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Investment Securities [Abstract]
Available for Sale, Amortized Cost - Due in one year or less	$ 200
Available for Sale, Amortized Cost - Due after five through ten years	35,490
Available for Sale, Amortized Cost - Due after ten years	2,806,104
Available for Sale, Amortized Cost - Totals	2,841,794
Available for Sale, Fair Value - Due in one year or less	200
Available for Sale, Fair Value - Due after five through ten years	26,199
Available for Sale, Fair Value - Due after ten years	2,838,918
Available for Sale, Fair Value - Totals	2,865,317
Held to Maturity, Amortized Cost - Due in one year or less	23,389
Held to Maturity, Amortized Cost - Due after one year through five years	9,860
Held to Maturity, Amortized Cost - Due after five through ten years	267,150
Held to Maturity, Amortized Cost - Due after ten years	2,673,328
Held to Maturity, Amortized Cost - Totals	2,973,727
Held to Maturity, Fair Value - Due in one year or less	23,394
Held to Maturity, Fair Value - Due after one year through five years	10,253
Held to Maturity, Fair Value - Due after five through ten years	283,956
Held to Maturity, Fair Value - Due after ten years	2,812,943
Held to Maturity, Fair Value - Totals	$ 3,130,546