Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Fees receivable	$ (126,358)	$ (111,946)
Interest Income, Related Party	100		$ 100
Due from related parties	26,749	33,870
Redeemable non-controlling interests, Related Party	391,275	216,923
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	(8,442)	(24,752)	(7,657)
Employees
Related Party Transaction [Line Items]
Redeemable non-controlling interests, Related Party	36,000	25,100
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	(7,900)	(7,600)	(7,200)
Employee Loans
Related Party Transaction [Line Items]
Due from employees	14,900	17,000
Forgivable Loan Balances	7,100	8,800
Amortization on Forgivable Loans	$ 3,800	3,100	2,100
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	$ (20,500)	(19,400)
Investor
Related Party Transaction [Line Items]
Due to Affiliate	300	600
Other Funds
Related Party Transaction [Line Items]
Due from related parties	5,300	$ 8,900
Starboard Value LP
Related Party Transaction [Line Items]
Effective interest rate		5.00%
Interest Income, Related Party	300	$ 400	$ 800
Due from related parties	$ 6,500	$ 7,700
Finance Period	5 years

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