Consolidated Company-Sponsored Investment Funds (Change in Carrying Value Associated with Level 3 Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	$ 115	$ 1,071	$ 142	$ 1,071
Purchases	0	0	0	0
Sales	0	0	0	0
Realized gains (losses), net	0	0	0	0
Unrealized gains (losses), net	2	(954)	(25)	(954)
Balance as of end of period	117	117	117	117
Company-sponsored investment funds
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	10,261	5,901	8,373	2,264
Transfers (out) in	(89)	337	(186)	324
Purchases	5,680	2,100	7,791	6,134
Sales	(4,065)	(2,290)	(4,349)	(2,623)
Realized gains (losses), net	21	(104)	23	(99)
Unrealized gains (losses), net	20	(75)	169	(133)
Accrued discounts	6	2	13	4
Balance as of end of period	$ 11,834	$ 5,871	$ 11,834	$ 5,871

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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

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-Publisher FASB
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-SubTopic 10
-Section 50
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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.

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Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

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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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-Publisher FASB
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Amount of accretion (amortization) of purchase discount (premium) on nonoperating securities.

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-Publisher FASB
-Name Accounting Standards Codification
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