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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Total revenue		$ 2,172	$ 2,254	$ 1,464	$ 4,681	$ 5,371	$ 5,284	$ 5,305	$ 5,012	$ 10,571	$ 20,972	$ 20,758
Equity in (losses) earnings	[1]									(141)	13	103
Equity Method Investment
Related Party Transaction [Line Items]
Total revenue										259	815	932
Equity in (losses) earnings										(141)	13	103
Reimbursements
Related Party Transaction [Line Items]
Total revenue	[1]									8,452	15,599	15,543
Reimbursed expenses	[1]									(8,435)	(16,439)	(15,778)
Reimbursements | Equity Method Investment
Related Party Transaction [Line Items]
Total revenue										107	233	332
Reimbursed expenses										$ (110)	$ (236)	$ (337)

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