Related Parties - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended
	Oct. 26, 2015	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Asset management fees		$ 272,924	$ 233,731
Fees receivable		439,836		$ 564,291
Payments under tax receivable agreement		736	10,086
Sponsored Funds [Member]
Related Party Transaction [Line Items]
Asset management fees		140,577	$ 118,910
Fees receivable		52,867		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%
Cumulative liability relating to obligations under Amended and Restated Tax Receivable Agreement		512,874		$ 513,610
Payments under tax receivable agreement		$ 736