Investments of Operating Entities and Consolidated Funds - Operating Entities - Gross Obligations For Securities Loaned And Securities Sold Under Agreements To Repurchase (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 3,083,945,000	$ 2,476,414,000
Securities sold, not yet purchased, at fair value	931,082,000	728,115,000
Common stock
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	2,827,291,000	2,232,687,000
Common stock | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	2,827,291,000	2,232,687,000
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	256,654,000	243,726,000
Securities sold, not yet purchased, at fair value	2,546,000	5,036,000
Corporate Bonds | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	256,654,000	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	2,546,000	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