Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Fees receivable	$ 157,606		$ 157,606		$ 160,349
Due from related parties	30,454		30,454		21,068
Redeemable non-controlling interests, Related Party	0		0		0
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	0	$ 0	0	$ (32,924)
Employees
Related Party Transaction [Line Items]
Redeemable non-controlling interests, Related Party	53,700		53,700		84,300
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	(3,900)	6,700	18,800	10,700
Employee Loans
Related Party Transaction [Line Items]
Due from employees	9,000		9,000		9,500
Forgivable Loan Balances	4,900		4,900		4,600
Amortization on Forgivable Loans	1,500	800	$ 4,300	2,800
Interest Income, Related Party				$ 100
Employee Loans | Minimum
Related Party Transaction [Line Items]
Forgivable Loans, Vesting Period			1 year
Employee Loans | Maximum
Related Party Transaction [Line Items]
Forgivable Loans, Vesting Period			3 years
Affiliated Entity
Related Party Transaction [Line Items]
Fees receivable	32,200		$ 32,200		28,400
Investor
Related Party Transaction [Line Items]
Due to Affiliate	200		200		200
Other Funds
Related Party Transaction [Line Items]
Due from related parties	$ 21,400		$ 21,400		7,900
Starboard Value LP
Related Party Transaction [Line Items]
Effective interest rate				5.00%
Interest Income, Related Party		$ 100		$ 200
Due from related parties					$ 3,600
Finance Period			5 years