ACQUISITIONS AND DISPOSITIONS - Disposals (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) investment property	Dec. 31, 2017 USD ($) property	Mar. 31, 2020 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of equity method investments disposed | investment		3
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
Number of properties disposed | property			3
Disposal Group, Disposed of by Sale, Not Discontinued Operations | St.Regis New York and The Sheraton Gateway Hotel
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal	$ 134
Disposal Group, Disposed of by Sale, Not Discontinued Operations | The Tremont Chicago Hotel at Magnificent Mile and Le Centre Sheraton Montreal Hotel
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | property		2
Disposal Group, Disposed of by Sale, Not Discontinued Operations | The Westin Denarau Island Resort and The Sheraton Fiji Resort
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | property		2
Disposal Group, Disposed of by Sale, Not Discontinued Operations | The Sheraton Buenos Aires Hotel & Convention Center and Park Tower and A Luxury Collection Hotel, Buenos Aires
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | property		2
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 | Charlotte Marriott City Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal			$ 24
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%
Gain on disposal, net of tax			$ 425
Procurement services term			5 years
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Sheraton Grand Phoenix
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal	15
Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets	248
Liabilities	8
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	118	115
Spending from sales proceeds,net of tax	$ 87	85
Sheraton Grand Phoenix
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration for property acquired		$ 255
Subsequent Event | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Sheraton Grand Phoenix
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration for property sold				$ 268