RELATED PARTY TRANSACTIONS - Financial Data Resulting from Transactions with Related Parties, Income Statement Data (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Total revenue		$ 5,371	$ 5,284	$ 5,305	$ 5,012	$ 5,289	$ 5,051	$ 5,409	$ 5,009	$ 20,972	$ 20,758	$ 20,452
Depreciation, amortization, and other	[1]									(341)	(226)	(229)
General, administrative, and other	[1]									(938)	(927)	(921)
Gains and other income, net	[1]									154	194	688
Interest expense	[1]									394	340	288
Interest income	[1]									26	22	38
Equity in earnings	[1]									13	103	40
Equity Method Investment
Related Party Transaction [Line Items]
Depreciation, amortization, and other										(2)	(2)	(3)
General, administrative, and other										(2)	0	(1)
Gains and other income, net										2	51	658
Interest expense										3	0	0
Interest income										0	0	4
Equity in earnings										13	103	40
Base management fees
Related Party Transaction [Line Items]
Gross fee revenues	[1]									1,180	1,140	1,102
Base management fees | Equity Method Investment
Related Party Transaction [Line Items]
Gross fee revenues										21	25	28
Incentive management fees
Related Party Transaction [Line Items]
Gross fee revenues	[1]									637	649	607
Incentive management fees | Equity Method Investment
Related Party Transaction [Line Items]
Gross fee revenues										8	12	15
Net fee revenues
Related Party Transaction [Line Items]
Gross fee revenues										3,823	3,638	3,295
Contract investment amortization	[1]									(62)	(58)	(50)
Total revenue										3,761	3,580	3,245
Net fee revenues | Equity Method Investment
Related Party Transaction [Line Items]
Contract investment amortization										(2)	(2)	(2)
Owned, leased, and other
Related Party Transaction [Line Items]
Total revenue	[1]									1,612	1,635	1,752
Reimbursed expenses										(1,316)	(1,306)	(1,411)
Owned, leased, and other | Equity Method Investment
Related Party Transaction [Line Items]
Total revenue										0	0	2
Reimbursements
Related Party Transaction [Line Items]
Total revenue	[1]									15,599	15,543	15,455
Reimbursed expenses	[1]									(16,439)	(15,778)	(15,228)
Reimbursements | Equity Method Investment
Related Party Transaction [Line Items]
Total revenue										233	332	356
Reimbursed expenses										$ (236)	$ (337)	$ (356)

[1] See Note 16 for disclosure of related party amounts.