Investments of Operating Entities and Consolidated Funds - Operating Entities - Gross Obligations For Securities Loaned And Securities Sold Under Agreements To Repurchase (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 2,476,414,000	$ 1,601,866,000
Securities sold, not yet purchased, at fair value	728,115,000	451,836,000
Common stock
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	2,232,687,000	1,343,478,000
Common stock | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	2,232,687,000	1,343,478,000
Common stock | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Common stock | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Common stock | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	243,726,000	258,388,000
Securities sold, not yet purchased, at fair value	5,036,000
Corporate Bonds | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	243,726,000	258,388,000
Securities sold, not yet purchased, at fair value	0
Corporate Bonds | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Securities sold, not yet purchased, at fair value	0
Corporate Bonds | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Securities sold, not yet purchased, at fair value	5,036,000
Corporate Bonds | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Securities sold, not yet purchased, at fair value	$ 0
Common Stock
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold, not yet purchased, at fair value		23,244,000
Common Stock | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold, not yet purchased, at fair value		0
Common Stock | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold, not yet purchased, at fair value		0
Common Stock | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold, not yet purchased, at fair value		23,244,000
Common Stock | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold, not yet purchased, at fair value		$ 0