Document and Entity Information
| Document and Entity Information | Mar. 06, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | EAGLE MATERIALS INC |
| Entity Incorporation State Country Code | DE |
| Entity Address, State or Province | TX |
| Amendment Flag | false |
| Entity Central Index Key | 0000918646 |
| Document Type | 8-K |
| Document Period End Date | Mar. 6, 2020 |
| Entity File Number | 1-12984 |
| Entity Tax Identification Number | 75-2520779 |
| Entity Address, Address Line One | 5960 BERKSHIRE LANE |
| Entity Address, Address Line Two | SUITE 900 |
| Entity Address, City or Town | DALLAS |
| Entity Address, Postal Zip Code | 75225 |
| City Area Code | (214) |
| Local Phone Number | 432-2000 |
| 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 | EXP |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |