Investments (Summary Of Gross Unrealized Gains And Losses And Fair Values) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 93,122	$ 154,214
Available-for-sale Securities, Gross Unrealized Gain	191	4,230
Available-for-sale Securities, Gross Unrealized Loss	(47)	(286)
Available-for-sale Securities	93,266	158,158
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	66,120	88,852
Available-for-sale Securities, Gross Unrealized Gain	186	110
Available-for-sale Securities, Gross Unrealized Loss	(31)	(213)
Available-for-sale Securities	66,275	88,749
Debt Securities Issued By The U.S Treasury And Other U.S Government Corporations And Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	19,070	40,715
Available-for-sale Securities, Gross Unrealized Gain	4	0
Available-for-sale Securities, Gross Unrealized Loss	(14)	(63)
Available-for-sale Securities	19,060	40,652
Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	5,532	6,111
Available-for-sale Securities, Gross Unrealized Gain	1	2
Available-for-sale Securities, Gross Unrealized Loss	(2)	(10)
Available-for-sale Securities	5,531	6,103
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		18,536
Available-for-sale Securities, Gross Unrealized Gain		4,118
Available-for-sale Securities, Gross Unrealized Loss		0
Available-for-sale Securities		$ 22,654
Variable Rate Demand Obligation [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,400
Available-for-sale Securities, Gross Unrealized Gain	0
Available-for-sale Securities, Gross Unrealized Loss	0
Available-for-sale Securities	$ 2,400

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)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 320
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-Section 50
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