| Document and Entity Information | Oct. 29, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 29, 2020 |
| Entity Registrant Name | Martin Marietta Materials, Inc. |
| Entity Incorporation State Country Code | NC |
| Entity File Number | 1-12744 |
| Entity Tax Identification Number | 56-1848578 |
| Entity Address, Address Line One | 2710 Wycliff Road |
| Entity Address, City or Town | Raleigh |
| Entity Address, State or Province | NC |
| Entity Address, Postal Zip Code | 27607 |
| City Area Code | 919 |
| Local Phone Number | 781-4550 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000916076 |
| Security 12b Title | Common Stock, $.01 par value per share |
| Trading Symbol | MLM |
| Security Exchange Name | NYSE |
