Fair Value Measurements - Classes of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financial Assets
Cash and Cash Equivalents	$ 383,180	$ 336,782
Investments—Consolidated Investment Companies	70,543	108,448
Investments—Affiliates and Other	106,952	76,524
Other	7,469	7,007
Total Financial Assets	568,144	528,761
Financial Liabilities
Total Financial Liabilities	7,626	8,470
Level 1
Financial Assets
Cash and Cash Equivalents	383,180	336,782
Investments—Consolidated Investment Companies	11,402	49,119
Investments—Affiliates and Other	104,341	71,369
Other	6,160	6,538
Total Financial Assets	505,083	463,808
Financial Liabilities
Total Financial Liabilities	0	27
Level 2
Financial Assets
Cash and Cash Equivalents	0	0
Investments—Consolidated Investment Companies	59,141	59,329
Investments—Affiliates and Other	2,588	5,130
Other	1,309	469
Total Financial Assets	63,038	64,928
Financial Liabilities
Total Financial Liabilities	0	4
Level 3
Financial Assets
Cash and Cash Equivalents	0	0
Investments—Consolidated Investment Companies	0	0
Investments—Affiliates and Other	23	25
Other	0	0
Total Financial Assets	23	25
Financial Liabilities
Total Financial Liabilities	$ 7,626	$ 8,439