Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total Fair value	$ 1,001,251	$ 1,114,454
Obligations Of States And Political Subdivisions [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Due within one year, Amortized cost	984
Securities Available-for-Sale, Due within one year, Fair value	995
Securities Available-for-Sale, Total Fair value	995	1,003
Securities Held-to-Maturity, Due within one year, Amortized cost	485
Securities Held-to-Maturity, Due within one year, Fair value	486
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	180,000
Securities Available-for-Sale, Due within one year, Fair value	180,338
Securities Available-for-Sale, Due one through five years, Amortized cost	173,750
Securities Available-for-Sale, Due one through five years, Fair value	171,548
Securities Available-for-Sale, Due five through ten years, Amortized cost	216,889
Securities Available-for-Sale, Due five through ten years, Fair value	216,134
Securities Available-for-Sale, Total, Amortized cost	570,639
Securities Available-for-Sale, Total Fair value	568,020	695,727
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	417,356
Securities Available-for-Sale, Total Fair value	429,867	415,502
Securities Held-to-Maturity, Total, Amortized cost	284,765
Securities Held-to-Maturity, Total, Fair value	$ 293,828