Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Associated With Level 3 Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2022	Sep. 30, 2022
Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 45,211	$ 64,706
Unrealized gains/(losses)		4,750
Realized gains	539	2,316
Purchases	1,559	3,149
Redemptions	2,193	29,805
Net change	(95)	(19,590)
Ending Balance	45,116	45,116
Corporate Equity Securities Financial Instruments Owned [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,013	225
Unrealized gains/(losses)		839
Realized gains		336
Sales		(387)
Net change	0	788
Ending Balance	1,013	1,013
Other Financial instruments owned [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	100,187	26,857
Unrealized gains/(losses)	338	550
Realized gains	225	793
Purchases	25,729	133,933
Sales	(51,824)	(85,042)
Redemptions	4,078	6,514
Net change	(29,610)	43,720
Ending Balance	70,577	70,577
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	11,878	5,754
Unrealized gains/(losses)		6,124
Net change	0	6,124
Ending Balance	11,878	11,878
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	13,965	13,032
Unrealized gains/(losses)	511	1,444
Net change	511	1,444
Ending Balance	14,476	14,476
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	34,779	35,837
Unrealized gains/(losses)	0	(1,012)
Realized gains	0	992
Sales		(999)
Redemptions		39
Net change	0	(1,058)
Ending Balance	$ 34,779	$ 34,779

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- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis realized asset gain loss included in earnings.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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- Definition

Amount of increase (decrease) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
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-Section 50
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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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