PROPERTY AND EQUIPMENT - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 256	$ 231	$ 157
Property and equipment, net	1,956	1,793
International Operations
Property, Plant and Equipment [Line Items]
Property and equipment, net	533	705
Reimbursed Expenses
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 147	$ 126	$ 76
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	40 years