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, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total Fair value	$ 1,265,477	$ 1,301,915
Securities Held-to-Maturity, Amortized Cost	133,383	140,562
Securities held-to-maturity, fair value	136,418	143,490
Obligations Of U.S. Treasury And Other U.S. Government Sponsored Entities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Due one through five years, Amortized cost	100,000
Securities Available-for-Sale, Due one through five years, Fair value	100,568
Available for Sale Securities Debt Maturities After One Through Five Years Weighted Avg Yield	2.11%
Securities Available-for-Sale, Due five through ten years, Amortized cost	396,887
Securities Available-for-Sale, Due five through ten years, Fair value	394,603
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Avg Yield	2.43%
Securities Available-for-Sale, Total, Amortized cost	496,887
Securities Available-for-Sale, Total Fair value	495,171	538,064
Available for Sale Securities Weighted Avg Yield	2.36%
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	753,444
Securities Available-for-Sale, Total Fair value	767,676	761,153
Available for Sale Securities Weighted Avg Yield	2.34%
Securities Held-to-Maturity, Amortized Cost	133,383	140,562
Securities held-to-maturity, fair value	$ 136,418	$ 143,490
Held to Maturity Securities weighted avg yield	3.51%