Investment Securities (Schedule Of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 1,074,605	$ 1,097,645
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	229	4,645
Securities Available-for-Sale, Gross Unrealized Holding Losses	42,569	10,409
Debt Securities, Available-for-sale	1,032,265	1,091,881
Securities Held-to-Maturity, Amortized Cost	350,642	357,197
Securities Held-to-Maturity, Gross Unrecognized Holding Gains	1,137	7,333
Securities Held-to-Maturity, Gross Unrecognized Holding Losses	7,438	751
Securities held-to-maturity, fair value	344,341	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	1,074,605	852,645
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	229	4,645
Securities Available-for-Sale, Gross Unrealized Holding Losses	42,569	8,129
Debt Securities, Available-for-sale	1,032,265	849,161
Securities Held-to-Maturity, Amortized Cost	46,974	56,785
Securities Held-to-Maturity, Gross Unrecognized Holding Gains	41	758
Securities Held-to-Maturity, Gross Unrecognized Holding Losses	1,386	38
Securities held-to-maturity, fair value	45,629	57,505
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Securities Held-to-Maturity, Amortized Cost	303,668	300,412
Securities Held-to-Maturity, Gross Unrecognized Holding Gains	1,096	6,575
Securities Held-to-Maturity, Gross Unrecognized Holding Losses	6,052	713
Securities held-to-maturity, fair value	$ 298,712	$ 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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