Fair Value Of Financial Instruments (Schedule Of Fair Value Of Investments In And Unfunded Commitments To Funds Measured At Net Asset Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items]
Fair value of investments	$ 37,512	$ 101,990
Unfunded commitments	2,854	3,155
Partnership Interests [Member]
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items]
Fair value of investments	4,519	5,124
Unfunded commitments	1,324	1,330
Mutual Funds [Member]
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items]
Fair value of investments	10,060	11,748
Private Equity Funds [Member]
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items]
Fair value of investments	5,050	7,677
Unfunded commitments	1,530	1,825
Money Market Funds [Member]
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items]
Fair value of investments	$ 17,883	$ 77,441

Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=SL6742756-110258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 35
-Paragraph 54B
-URI http://asc.fasb.org/extlink&oid=99392525&loc=SL7495116-110257

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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.

+ References

No definition available.

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- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=SL6742756-110258

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