DISPOSITIONS AND ACQUISITIONS - Disposals (Details) - USD ($) $ in Millions	12 Months Ended		24 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal of equity method investment	$ 42
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal	132
Disposal Group, Disposed of by Sale, Not Discontinued Operations | JW Marriott Mexico City
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal from equity method investee	55
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Ritz Carlton Toronto
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal from equity method investee	10
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Avendra LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal	5	$ 659
Ownership percentage		55.00%
Procurement services term		5 years
Gain on disposal, net of tax			$ 425
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Charlotte Marriott City Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal		$ 24
Reimbursed Expenses | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Avendra LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Spending from sales proceeds	115
Spending from sales proceeds,net of tax	$ 85