| Document and Entity Information Document | Apr. 30, 2021 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Apr. 30, 2021 |
| Entity Registrant Name | Exxon Mobil Corporation |
| Entity Incorporation, State or Country Code | NJ |
| Entity File Number | 1-2256 |
| Entity Tax Identification Number | 13-5409005 |
| Entity Address, Address Line One | 5959 Las Colinas Boulevard |
| Entity Address, City or Town | Irving |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 75039-2298 |
| City Area Code | 972 |
| Local Phone Number | 940-6000 |
| Written Communications | false |
| Soliciting Material | true |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000034088 |
| Amendment Flag | false |
| Common Stock, without par value | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock, without par value |
| Trading Symbol | XOM |
| Security Exchange Name | NYSE |
| 0.142% Notes due 2024 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 0.142% Notes due 2024 |
| Trading Symbol | XOM24B |
| Security Exchange Name | NYSE |
| 0.524% Notes due 2028 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 0.524% Notes due 2028 |
| Trading Symbol | XOM28 |
| Security Exchange Name | NYSE |
| 0.835% Notes due 2032 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 0.835% Notes due 2032 |
| Trading Symbol | XOM32 |
| Security Exchange Name | NYSE |
| 1.408% Notes due 2039 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 1.408% Notes due 2039 |
| Trading Symbol | XOM39A |
| Security Exchange Name | NYSE |
