| Document And Entity Information | Feb. 25, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 25, 2021 |
| Entity Registrant Name | Cars.com Inc. |
| Entity Central Index Key | 0001683606 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-37869 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 81-3693660 |
| Entity Address, Address Line One | 300 S. Riverside Plaza |
| Entity Address, Address Line Two | Suite 1000 |
| Entity Address, City or Town | Chicago |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60606 |
| City Area Code | 312 |
| Local Phone Number | 601-5000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | CARS |
| Security Exchange Name | NYSE |
