Related Party Transactions - Management Fees and Incentive Income Earned from Related Parties and Waived Fees (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Management fees
Related Party Transaction [Line Items]
Investment management revenues	$ 60,383	$ 61,400	$ 127,336	$ 125,023
Incentive Income
Related Party Transaction [Line Items]
Investment management revenues	38,238	34,757	47,560	87,955
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	833	1,671	1,899	4,396
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	$ 94	$ 3,207	$ 431	$ 4,768