| Document and Entity Information | Mar. 17, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | EXXON MOBIL CORP |
| Entity Address, State or Province | TX |
| Amendment Flag | false |
| Entity Central Index Key | 0000034088 |
| Document Type | 8-K |
| Document Period End Date | Mar. 17, 2020 |
| Entity Incorporation State 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, Postal Zip Code | 75039-2298 |
| City Area Code | (972) |
| Local Phone Number | 940-6000 |
| Security 12b Title | Common Stock, without par value |
| Trading Symbol | XOM |
| Security Exchange Name | NYSE |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
