Related Parties - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 26, 2015	Jul. 31, 2015	Jun. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Asset management fees					$ 1,195,550	$ 998,887	$ 1,036,821
Fees receivable					$ 487,800	$ 564,291
Tax receivable agreement, expiration terms					The term of the Amended and Restated Tax Receivable Agreement will continue until approximately 2033 or, if earlier, until all relevant tax benefits have been utilized or expired.
Provision (benefit) pursuant to tax receivable agreement			$ 961,948		$ (202,546)		$ 547,691
Percentage of beneficial interests purchased in trust		47.00%
Payments to cancel beneficial interests and extinguishment of payment obligations under the amended and restated tax receivable agreement		$ 42,222
U.S. federal statutory income tax rate					35.00%	35.00%	35.00%
Payments under tax receivable agreement					$ 789	$ 10,086	$ 1,276
Scenario Forecast [Member]
Related Party Transaction [Line Items]
U.S. federal statutory income tax rate				21.00%
Sponsored Funds [Member]
Related Party Transaction [Line Items]
Asset management fees					649,089	516,667	534,752
Fees receivable					69,107	49,944
LTBP Trust [Member]
Related Party Transaction [Line Items]
Amount of cash savings in income or franchise tax that would be realized as a result of increases in tax basis and certain other tax benefits related to the amended and restated tax receivable agreement	45.00%
Cash tax saving that may arise from tax benefits attributable to payments under the amended and restated tax receivable agreement	85.00%
Provision (benefit) pursuant to tax receivable agreement					(202,546)		547,691
Pre-tax gain on extinguishment of obligations under tax receivable agreement							420,792
Reduction of deferred tax benefit related to tax receivable agreement							$ 161,000
Reduction in tax receivable agreement obligation					202,546
Cumulative liability relating to obligations under Amended and Restated Tax Receivable Agreement					310,275	$ 513,610
Payments under tax receivable agreement					$ 789