Investment Securities (Schedule Of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 1,127,511	$ 1,097,645
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	476	4,645
Securities Available-for-Sale, Gross Unrealized Holding Losses	36,309	10,409
Debt Securities, Available-for-sale	1,091,678	1,091,881
Securities Held-to-Maturity, Amortized Cost	351,431	357,197
Securities Held-to-Maturity, Gross Unrecognized Holding Gains	2,320	7,333
Securities Held-to-Maturity, Gross Unrecognized Holding Losses	5,559	751
Securities held-to-maturity, fair value	348,192	363,779
Obligations Of U.S. Treasury And Other U.S. Government Sponsored Entities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		245,000
Securities Available-for-Sale, Gross Unrealized Holding Losses		2,280
Debt Securities, Available-for-sale		242,720
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,127,511	852,645
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	476	4,645
Securities Available-for-Sale, Gross Unrealized Holding Losses	36,309	8,129
Debt Securities, Available-for-sale	1,091,678	849,161
Securities Held-to-Maturity, Amortized Cost	47,192	56,785
Securities Held-to-Maturity, Gross Unrecognized Holding Gains	95	758
Securities Held-to-Maturity, Gross Unrecognized Holding Losses	1,236	38
Securities held-to-maturity, fair value	46,051	57,505
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Securities Held-to-Maturity, Amortized Cost	304,239	300,412
Securities Held-to-Maturity, Gross Unrecognized Holding Gains	2,225	6,575
Securities Held-to-Maturity, Gross Unrecognized Holding Losses	4,323	713
Securities held-to-maturity, fair value	$ 302,141	$ 306,274

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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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