| Document and Entity Information | Oct. 05, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | General Motors Co |
| Entity Incorporation State Country Code | DE |
| Amendment Flag | false |
| Entity Central Index Key | 0001467858 |
| Document Type | 8-K |
| Document Period End Date | Oct. 5, 2021 |
| Entity File Number | 001-34960 |
| Entity Tax Identification Number | 27-0756180 |
| Entity Address, Address Line One | 300 Renaissance Center |
| Entity Address, City or Town | Detroit |
| Entity Address, State or Province | MI |
| Entity Address, Postal Zip Code | 48265-3000 |
| City Area Code | (313) |
| Local Phone Number | 667-1500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.01 par value |
| Trading Symbol | GM |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
