Unconsolidated Entities - Summary of Strategic Capital Revenues Recognized in Consolidated Statements of Income Related to Co-Investment Ventures (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule Of Equity Method Investments [Line Items]
Total revenues	$ 682,432	$ 602,874	$ 1,997,364	$ 1,998,212
Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Recurring fees	58,946	52,684	171,508	140,357
Transactional fees	11,798	14,967	39,250	36,186
Promote revenues	0	0	68,218	127,092
Total revenues	$ 70,744	$ 67,651	$ 278,976	$ 303,635