Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total Fair value	$ 1,224,849	$ 1,436,266
Securities Held-to-Maturity, Amortized Cost	195,095	149,302
Securities held-to-maturity, fair value	200,538	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	113,283
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	116,860
Securities Held-to-Maturity, Amortized Cost	113,283	48,190
Securities held-to-maturity, fair value	$ 116,860	48,924
Held to Maturity Securities weighted avg yield	4.35%
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	$ 270,000
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	$ 269,145
Available for Sale Securities Debt Maturities two through five Weighted Avg Yield	1.18%
Securities Available-for-Sale, Total, Amortized cost	$ 270,000
Securities Available-for-Sale, Total Fair value	$ 269,145	522,063
Available for Sale Securities Weighted Avg Yield	1.18%
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	$ 932,869
Securities Available-for-Sale, Total Fair value	$ 952,897	911,493
Available for Sale Securities Weighted Avg Yield	2.13%
Securities Held-to-Maturity, Amortized Cost	$ 81,812	101,112
Securities held-to-maturity, fair value	$ 83,678	$ 102,504
Held to Maturity Securities weighted avg yield	3.31%