Investments Of Operating Entities And Consolidated Funds - Operating Entities - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative [Line Items]
Receivable from brokers, dealers and clearing organizations, net of allowance of $792 and $721, respectively	$ 773,317		$ 681,695
Payables to brokers, dealers and clearing organizations	330,096		271,018
Receivables from Brokers-Dealers and Clearing Organizations
Derivative [Line Items]
Collateral posted	12,900		$ 10,500
Other Income [Member]
Derivative [Line Items]
Realized and unrealized gains/(losses) related to derivatives trading activities	$ 28,800	$ (2,200)

Amount payable to other broker-dealer and clearing organization, including, but not limited to, security failed-to-receive, deposit received for security loaned, open transaction, and floor-brokerage payable.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
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Aggregate net gain and losses (whether realized or unrealized) on all derivative instruments held for trading purposes whether or not settled physically.

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Amount receivable from broker-dealers and clearing organizations, including, but not limited to, securities failed-to-deliver, certain deposits for securities borrowed, open transactions, good faith and margin deposits, commissions and floor brokerage receivables.

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