BUSINESS SEGMENTS - Capital Expenditures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Capital expenditures	$ 556	$ 240	$ 199
Total segment | North American Full-Service
Segment Reporting Information [Line Items]
Capital expenditures	290	21	35
Total segment | North American Limited-Service
Segment Reporting Information [Line Items]
Capital expenditures	15	10	7
Total segment | Asia Pacific
Segment Reporting Information [Line Items]
Capital expenditures	6	12	1
Total segment | Other International
Segment Reporting Information [Line Items]
Capital expenditures	40	42	38
Unallocated corporate
Segment Reporting Information [Line Items]
Capital expenditures	$ 205	$ 155	$ 118