Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Fees receivable	$ 160,349	$ 126,358
Interest Income, Related Party	100	100
Due from related parties	21,068	26,749
Redeemable non-controlling interests, Related Party	0	391,275
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	(32,924)	8,442	$ 24,752
Employees
Related Party Transaction [Line Items]
Redeemable non-controlling interests, Related Party	84,300	36,000
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	21,200	7,900	7,600
Employee Loans
Related Party Transaction [Line Items]
Due from employees	9,500	14,900
Forgivable Loan Balances	4,600	7,100
Amortization on Forgivable Loans	$ 3,700	3,800	3,100
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	$ 28,400	20,500
Investor
Related Party Transaction [Line Items]
Due to Affiliate	200	300
Other Funds
Related Party Transaction [Line Items]
Due from related parties	7,900	$ 5,300
Starboard Value LP
Related Party Transaction [Line Items]
Effective interest rate		5.00%
Interest Income, Related Party	200	$ 300	$ 400
Due from related parties	$ 3,600	$ 6,500
Finance Period	5 years

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