Investment Securities (Schedule Of Investment Securities Classified As Available-for-sale And Held-to-maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale [Abstract]
Amortized cost	$ 1,071,586	$ 1,473,524
Gross unrealized gains	7,235	24,375
Gross unrealized losses	(8,723)	(4,260)
Fair value	1,070,098	1,493,639
Held-to-maturity [Abstract]
Amortized cost	93,590	93,765
Gross unrealized gains	1,507	1,969
Gross unrealized losses	(3,498)	(3,820)
Fair value	91,599	91,914
U.S. Government Agency Securities [Member]
Available-for-sale [Abstract]
Amortized cost	29,315	16,519
Gross unrealized gains	18	42
Gross unrealized losses	(95)
Fair value	29,238	16,561
Federally insured student loan securities [Member]
Available-for-sale [Abstract]
Amortized cost	118,651	125,789
Gross unrealized gains	28	613
Gross unrealized losses	(3,530)	(390)
Fair value	115,149	126,012
Tax-exempt Obligations Of States And Political Subdivisions [Member]
Available-for-sale [Abstract]
Amortized cost	94,572	535,622
Gross unrealized gains	2,665	16,027
Gross unrealized losses	(74)	(380)
Fair value	97,163	551,269
Taxable obligations of states and political subdivisions [Member]
Available-for-sale [Abstract]
Amortized cost	95,802	58,868
Gross unrealized gains	2,370	2,614
Gross unrealized losses	(476)	(103)
Fair value	97,696	61,379
Residential Mortgage-backed Securities [Member]
Available-for-sale [Abstract]
Amortized cost	451,432	419,503
Gross unrealized gains	1,540	3,504
Gross unrealized losses	(2,865)	(878)
Fair value	450,107	422,129
Commercial Mortgage-backed Securities [Member]
Available-for-sale [Abstract]
Amortized cost	58,512	123,519
Gross unrealized gains	361	1,220
Gross unrealized losses	(570)	(1,500)
Fair value	58,303	123,239
Commercial Loan Obligation Securities [Member]
Available-for-sale [Abstract]
Amortized cost	70,573
Gross unrealized losses	(81)
Fair value	70,492
Foreign Debt Securities [Member]
Available-for-sale [Abstract]
Amortized cost	57,375	67,094
Gross unrealized gains	65	130
Gross unrealized losses	(308)	(346)
Fair value	57,132	66,878
Corporate And Other Debt Securities [Member]
Available-for-sale [Abstract]
Amortized cost	95,354	126,610
Gross unrealized gains	188	225
Gross unrealized losses	(724)	(663)
Fair value	94,818	126,172
Single Issuers [Member]
Held-to-maturity [Abstract]
Amortized cost	17,934	17,882
Gross unrealized gains	569	531
Gross unrealized losses	(3,456)	(3,820)
Fair value	15,047	14,593
Pooled [Member]
Held-to-maturity [Abstract]
Amortized cost	75,656	75,883
Gross unrealized gains	938	1,438
Gross unrealized losses	(42)
Fair value	$ 76,552	$ 77,321

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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-Publisher FASB
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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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