Unit Capital - Summary of Transactions with Respect to the Company's Units (Detail)	6 Months Ended
	Jun. 30, 2020 shares
Capital Unit [Line Items]
Units Outstanding, Beginning Balance	46,143,564
Units Issued During the Period	905,388
Units Repurchased During the Period	(584,343)
Units Outstanding, Ending Balance	46,464,609
Class A Units [Member]
Capital Unit [Line Items]
Units Outstanding, Beginning Balance	17,861,312
Units Issued During the Period	254,288
Units Repurchased During the Period	(205,662)
Units Outstanding, Ending Balance	17,909,938
Class C Units [Member]
Capital Unit [Line Items]
Units Outstanding, Beginning Balance	8,067,787
Units Issued During the Period	31,003
Units Repurchased During the Period	(115,855)
Units Outstanding, Ending Balance	7,982,935
Class I Units [Member]
Capital Unit [Line Items]
Units Outstanding, Beginning Balance	10,468,162
Units Issued During the Period	297,965
Units Repurchased During the Period	(259,650)
Units Outstanding, Ending Balance	10,506,478
Class W Units [Member]
Capital Unit [Line Items]
Units Outstanding, Beginning Balance	24,555
Units Outstanding, Ending Balance	24,555
Class Y Units [Member]
Capital Unit [Line Items]
Units Outstanding, Beginning Balance	1,297,897
Units Issued During the Period	322,131
Units Repurchased During the Period	(3,176)
Units Outstanding, Ending Balance	1,616,852
Class Z Units [Member]
Capital Unit [Line Items]
Units Outstanding, Beginning Balance	8,423,851
Units Outstanding, Ending Balance	8,423,851