Cover Page
| Cover Page - USD ($) | 12 Months Ended | ||
| Dec. 31, 2020 | Feb. 10, 2021 | Jun. 30, 2020 | |
| Cover [Abstract] | |||
| Document Type | 10-K/A | ||
| 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 |