Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Fair value	$ 797,163	$ 1,297,522
Obligations Of U.S. Treasury And Other U.S. Government Sponsored Entities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Due within one year, Amortized cost	223,459
Securities Available-for-Sale, Due within one year, Fair value	224,817
Securities Available-for-Sale, Total, Amortized cost	223,459
Securities Available-for-Sale, Total, Fair value	224,817	273,313
Obligations Of States And Political Subdivisions [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Due within one year, Amortized cost	2,315
Securities Available-for-Sale, Due within one year, Fair value	2,327
Securities Available-for-Sale, Due one through five years, Amortized cost	1,300
Securities Available-for-Sale, Due one through five years, Fair value	1,397
Securities Available-for-Sale, Total, Amortized cost	3,615
Securities Available-for-Sale, Total, Fair value	3,724	11,044
Securities Held-to-Maturity, Due within one year, Amortized cost	1,992
Securities Held-to-Maturity, Due within one year, Fair value	1,999
Securities Held-to-Maturity, Total, Amortized cost	1,992
Securities Held-to-Maturity, Total, Fair value	1,999
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	544,648
Securities Available-for-Sale, Total, Fair value	566,748	1,011,412
Securities Held-to-Maturity, Total, Amortized cost	841,584
Securities Held-to-Maturity, Total, Fair value	$ 859,370