Related Party Transactions - Management Fees and Incentive Income Earned from Related Parties and Waived Fees (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Management fees
Related Party Transaction [Line Items]
Investment management revenues	$ 253,011	$ 281,862	$ 319,458
Incentive Income
Related Party Transaction [Line Items]
Investment management revenues	321,621	202,896	528,000
Fees charged on investments held by related parties: | Management fees | Executive Managing Directors, Employees and Other Related Parties
Related Party Transaction [Line Items]
Investment management revenues	7,324	14,017	10,574
Fees charged on investments held by related parties: | Incentive Income | Executive Managing Directors, Employees and Other Related Parties
Related Party Transaction [Line Items]
Investment management revenues	$ 8,749	$ 7,530	$ 14,052