Consolidated Company-Sponsored Investment Funds - Change in Carrying Value Associated with Level 3 Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	$ 1,071	$ 5,023
Purchases	0	0
Sales	0	0
Realized (losses) gains, net	0	0
Unrealized (losses) gains, net	(929)	(3,952)
Balance as of end of period	142	1,071
Company-Sponsored Investment Funds
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	2,264	5,741
Deconsolidated funds	0	(7,267)
Transfers in	259	480
Purchases	9,354	6,127
Sales	(3,086)	(3,120)
Realized (losses) gains, net	(100)	2
Unrealized (losses) gains, net	(331)	286
Accrued discounts	13	15
Balance as of end of period	$ 8,373	$ 2,264

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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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 the income statement for 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 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.

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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.

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

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