Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	$ 1,074,605	$ 1,097,645
Securities Available-for-Sale, Total Fair value	1,032,265	1,091,881
Securities Held-to-Maturity, Amortized Cost	350,642	357,197
Securities held-to-maturity, fair value	344,341	363,779
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	2,430
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	$ 2,385
Held to Maturity Securities weighted avg yield five through ten	2.97%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 301,238
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	$ 296,327
Held to Maturity Securities Debt Maturities Years Over Ten weighted avg yield	3.68%
Securities Held-to-Maturity, Amortized Cost	$ 303,668	300,412
Securities held-to-maturity, fair value	$ 298,712	306,274
Held to Maturity Securities weighted avg yield	3.67%
Obligations Of U.S. Treasury And Other U.S. Government Sponsored Entities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost		245,000
Securities Available-for-Sale, Total Fair value		242,720
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Securities Available-for-Sale, Total, Amortized cost	$ 1,074,605	852,645
Securities Available-for-Sale, Total Fair value	$ 1,032,265	849,161
Available for Sale Securities Weighted Avg Yield	2.35%
Securities Held-to-Maturity, Amortized Cost	$ 46,974	56,785
Securities held-to-maturity, fair value	$ 45,629	$ 57,505
Held to Maturity Securities weighted avg yield	2.83%

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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