| Document and Entity Information | Feb. 20, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | LAMAR ADVERTISING CO/NEW |
| Amendment Flag | false |
| Entity Central Index Key | 0001090425 |
| Document Type | 8-K |
| Document Period End Date | Feb. 20, 2020 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-36756 |
| Entity Tax Identification Number | 72-1449411 |
| Entity Address, Address Line One | 5321 Corporate Blvd. |
| Entity Address, City or Town | Baton Rouge |
| Entity Address, State or Province | LA |
| Entity Address, Postal Zip Code | 70808 |
| City Area Code | (225) |
| Local Phone Number | 926-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Class A common stock, $0.001 par value |
| Trading Symbol | LAMR |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
