Investments - Gains and Losses Recognized in Gain (Loss) on Securities, Net (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Gain (Loss) on Securities, net	$ 4,966	$ (4,357)	$ 8,072
Investments—Consolidated Investment Companies
Gain (Loss) on Securities [Line Items]
Unrealized Gains (Losses)	4,759	(3,142)	771
Net Realized Gains (Losses)	(1,243)	(374)	2,245
Gain (Loss) on Securities, net	3,516	(3,516)	3,016
Investments—Affiliates and Other
Gain (Loss) on Securities [Line Items]
Unrealized Gains (Losses)	2,156	(1,180)	118
Net Realized Gains (Losses)	(706)	339	4,938
Gain (Loss) on Securities, net	$ 1,450	$ (841)	$ 5,056

The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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Amount of unrealized gain (loss) on investment in marketable security.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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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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