Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total Fair value	$ 1,372,183	$ 1,436,266
Securities Held-to-Maturity, Amortized Cost	171,273	149,302
Securities held-to-maturity, fair value	174,528	151,428
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	75,144
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	76,571
Securities Held-to-Maturity, Amortized Cost	75,144	48,190
Securities held-to-maturity, fair value	$ 76,571	48,924
Held to Maturity Securities weighted avg yield	4.54%
Obligations Of U.S. Treasury And Other U.S. Government Sponsored Entities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	$ 320,000
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	$ 319,717
Available for Sale Securities Debt Maturities two through five Weighted Avg Yield	1.18%
Securities Available-for-Sale, Due five through ten years, Amortized cost	$ 101,897
Securities Available-for-Sale, Due five through ten years, Fair value	$ 101,493
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Avg Yield	2.33%
Securities Available-for-Sale, Total, Amortized cost	$ 421,897
Securities Available-for-Sale, Total Fair value	$ 421,210	522,063
Available for Sale Securities Weighted Avg Yield	1.46%
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	$ 931,644
Securities Available-for-Sale, Total Fair value	$ 948,351	911,493
Available for Sale Securities Weighted Avg Yield	2.20%
Securities Held-to-Maturity, Amortized Cost	$ 96,129	101,112
Securities held-to-maturity, fair value	$ 97,957	$ 102,504
Held to Maturity Securities weighted avg yield	3.34%