| Document and Entity Information | Oct. 27, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | SONIC AUTOMOTIVE INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001043509 |
| Document Type | 8-K |
| Document Period End Date | Oct. 27, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-13395 |
| Entity Tax Identification Number | 56-2010790 |
| Entity Address, Address Line One | 4401 Colwick Road |
| Entity Address, City or Town | Charlotte |
| Entity Address, State or Province | NC |
| Entity Address, Postal Zip Code | 28211 |
| City Area Code | (704) |
| Local Phone Number | 566-2400 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Class A Common Stock, par value $0.01 per share |
| Trading Symbol | SAH |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
