Investments - Gains and Losses Recognized in Gain (Loss) on Securities, Net (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
(Loss) Gain on Securities [Line Items]
Gain (Loss) on Securities, net	$ 577	$ (815)	$ 2,256	$ (1,997)
Investments—Consolidated Investment Companies
(Loss) Gain on Securities [Line Items]
Unrealized Gains (Losses)	424	(653)	1,709	(2,343)
Realized Gains	53	501	160	1,325
Realized Losses	(259)	(723)	(827)	(898)
Gain (Loss) on Securities, net	218	(875)	1,042	(1,916)
Investments—Affiliates and Other
(Loss) Gain on Securities [Line Items]
Unrealized Gains (Losses)	340	9	1,217	(206)
Net Realized Gains (Losses) Recognized on Securities Sold	19	51	(3)	125
Gain (Loss) on Securities, net	$ 359	$ 60	$ 1,214	$ (81)

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.

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The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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The difference between the carrying value and the sale price of an investment. A loss would be recognized when the sale price of the investment is less than the carrying value of the investment. This element refers to the Loss included in earnings and not to the cash proceeds of the sale.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(9)(a))
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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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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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