Investments of Operating Entities and Consolidated Funds - Operating Entities - Gross Obligations For Securities Loaned And Securities Sold Under Agreements To Repurchase (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 3,352,456,000	$ 2,476,414,000
Securities sold, not yet purchased, at fair value	1,361,723,000	728,115,000
Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	400,238,000	243,726,000
Securities sold, not yet purchased, at fair value	29,063,000	5,036,000
Corporate Bonds | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	400,238,000	243,726,000
Securities sold, not yet purchased, at fair value	0	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	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	29,063,000	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	0
Common Stock
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	3,079,434,000	2,232,688,000
Common Stock | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	3,079,434,000	2,232,688,000
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