| 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 | true |
| Entity Central Index Key | 0000918646 |
| Document Type | 8-K/A |
| 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 |
| Amendment Description | Eagle Materials Inc., a Delaware corporation (the “Company”), is filing this Current Report on Form 8-K/A (this “Amendment No. 1”) in order to file the historical financial statements and pro forma financial information required by Items 9.01 (a) and (b) of Form 8-K, as well as the independent auditor consent, which were omitted as permitted in paragraphs (a)(4) and (b)(2) of such Item from its Current Report on Form 8-K, filed with the Securities and Exchange Commission (the “Commission”) on March 6, 2020 (the “Original Form 8-K”) in connection with the acquisition of certain assets (the “Acquisition”) of Kosmos Cement Company, a Kentucky general partnership (the “Seller”). The financial statements and information filed with this Amendment No. 1 consist of the historical financial statements of the Seller specified in Rule 3-05(b) of Regulation S-X and the pro forma financial information required in connection with the Acquisition pursuant to Article 11 of Regulation S-X. The pro forma financial information included in this Amendment No. 1 has been presented for informational purposes only, as required by Form 8-K; it does not purport to represent the actual results of operations that the Company would have achieved had it completed the Acquisition prior to the periods presented in the pro forma financial information and it is not intended to project the future results of operations that the Company may achieve after the Acquisition. |
