LEASES - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) renewal_option	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Lease term	20 years
Number of renewals (or more than) | renewal_option	1
Term of lease not commenced	20 years
U.S. and Canada Leased Hotels
Lessee, Lease, Description [Line Items]
Impairment loss	$ 116	$ 99
Legacy-Starwood Office Building
Lessee, Lease, Description [Line Items]
Impairment loss from building accounted for as a finance lease		$ 34
Minimum
Lessee, Lease, Description [Line Items]
Renewal term	5 years
Maximum
Lessee, Lease, Description [Line Items]
Renewal term	10 years