v3.19.1
Document and Entity Information - USD ($)
$ in Billions
12 Months Ended
Mar. 31, 2019
May 21, 2019
Sep. 30, 2018
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Mar. 31, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Trading Symbol EXP    
Entity Registrant Name EAGLE MATERIALS INC    
Entity Central Index Key 0000918646    
Current Fiscal Year End Date --03-31    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Common Stock, Shares Outstanding   44,117,946  
Entity Public Float     $ 4.0