Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total Fair value	$ 1,305,574	$ 1,436,266
Securities Held-to-Maturity, Amortized Cost	184,121	149,302
Securities held-to-maturity, fair value	191,557	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	94,164
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	99,568
Securities Held-to-Maturity, Amortized Cost	94,164	48,190
Securities held-to-maturity, fair value	$ 99,568	48,924
Held to Maturity Securities weighted avg yield	4.45%
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	$ 345,000
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	$ 345,362
Available for Sale Securities Debt Maturities two through five Weighted Avg Yield	1.24%
Securities Available-for-Sale, Due five through ten years, Amortized cost	$ 15,000
Securities Available-for-Sale, Due five through ten years, Fair value	$ 15,005
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Avg Yield	2.20%
Securities Available-for-Sale, Total, Amortized cost	$ 360,000
Securities Available-for-Sale, Total Fair value	$ 360,367	522,063
Available for Sale Securities Weighted Avg Yield	1.28%
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	$ 920,237
Securities Available-for-Sale, Total Fair value	$ 942,579	911,493
Available for Sale Securities Weighted Avg Yield	2.17%
Securities Held-to-Maturity, Amortized Cost	$ 89,957	101,112
Securities held-to-maturity, fair value	$ 91,989	$ 102,504
Held to Maturity Securities weighted avg yield	3.35%