Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 10, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	1-13881
Entity Registrant Name	MARRIOTT INTERNATIONAL INC /MD/
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-2055918
Entity Address, Address Line One	10400 Fernwood Road
Entity Address, City or Town	Bethesda
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20817
City Area Code	301
Local Phone Number	380-3000
Title of 12(b) Security	Class A Common Stock, $0.01 par value
Trading Symbol	MAR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 23,156,431,539
Entity Common Stock, Shares Outstanding		324,414,150
Documents Incorporated by Reference	Portions of the Proxy Statement prepared for the 2021 Annual Meeting of Stockholders are incorporated by reference into Part III of this report.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001048286
Current Fiscal Year End Date	--12-31