Related Party Transactions - Management Fees and Incentive Income Earned from Related Parties and Waived Fees (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Related Party Transaction [Line Items]
Management fees	$ 86,255	$ 156,910
Incentive income	51,626	30,587
Fees charged on investments held by related parties:
Related Party Transaction [Line Items]
Management fees	2,691	4,767
Incentive income	$ 1,878	$ 920