Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total Fair value	$ 1,293,464	$ 1,301,915
Securities Held-to-Maturity, Amortized Cost	117,509	140,562
Securities held-to-maturity, fair value	119,585	143,490
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	6,094
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	6,142
Securities Held-to-Maturity, Amortized Cost	6,094
Securities held-to-maturity, fair value	$ 6,142
Held to Maturity Securities weighted avg yield	5.03%
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	$ 150,000
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	$ 150,257
Available for Sale Securities Debt Maturities two through five Weighted Avg Yield	1.39%
Securities Available-for-Sale, Due five through ten years, Amortized cost	$ 396,888
Securities Available-for-Sale, Due five through ten years, Fair value	$ 394,794
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Avg Yield	2.43%
Securities Available-for-Sale, Total, Amortized cost	$ 546,888
Securities Available-for-Sale, Total Fair value	$ 545,051	538,064
Available for Sale Securities Weighted Avg Yield	2.14%
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	$ 734,014
Securities Available-for-Sale, Total Fair value	$ 745,780	761,153
Available for Sale Securities Weighted Avg Yield	2.31%
Securities Held-to-Maturity, Amortized Cost	$ 111,415	140,562
Securities held-to-maturity, fair value	$ 113,443	$ 143,490
Held to Maturity Securities weighted avg yield	3.49%