| Cover - shares | 3 Months Ended | |
| Mar. 31, 2021 | Apr. 30, 2021 | |
| Cover [Abstract] | ||
| Document Type | 10-Q/A | |
| Document Quarterly Report | true | |
| Document Period End Date | Mar. 31, 2021 | |
| Document Transition Report | false | |
| Entity File Number | 1-1513 | |
| Entity Registrant Name (tagged on cover) | Marathon Oil Corporation | |
| Entity Incorporation, State or Country Code | DE | |
| Entity Tax Identification Number | 25-0996816 | |
| Entity Address, Address Line One | 990 Town and Country Boulevard | |
| Entity Address, City or Town | Houston | |
| Entity Address, State or Province | TX | |
| Entity Address, Postal Zip Code | 77024-2217 | |
| City Area Code | 713 | |
| Local Phone Number | 629-6600 | |
| Title of 12(b) Security | Common Stock, par value $1.00 | |
| Trading Symbol | MRO | |
| Security Exchange Name | NYSE | |
| 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 | |
| Entity Shell Company | false | |
| Entity Common Stock, Shares Outstanding | 788,153,032 | |
| Document Fiscal Period Focus | Q1 | |
| Document Fiscal Year Focus | 2021 | |
| Amendment Flag | false | |
| Entity Central Index Key | 0000101778 | |
| Current Fiscal Year End Date | --12-31 |
