v3.26.1
Cover - USD ($)
$ in Billions
 12 Months Ended
Mar. 31, 2026
Apr. 30, 2026
Sep. 30, 2025
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Current Fiscal Year End Date --03-31    
Document Period End Date Mar. 31, 2026    
Document Transition Report false    
Entity File Number 1-15240    
Entity Registrant Name JAMES HARDIE INDUSTRIES plc    
Entity Incorporation, State or Country Code L2    
Entity Tax Identification Number 98-0382260    
Entity Address, Address Line One 1st Floor, Block A    
Entity Address, Address Line Two One Park Place    
Entity Address, Address Line Three Upper Hatch Street    
Entity Address, City or Town Dublin 2    
Entity Address, Postal Zip Code D02 FD79    
Entity Address, Country IE    
City Area Code 353    
Local Phone Number 1411 6924    
Title of 12(b) Security Ordinary shares, 0.59 Euro par value per share    
Trading Symbol JHX    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 11.1
Entity Common Stock, Shares Outstanding   580,314,579  
Documents Incorporated by Reference
DOCUMENTS INCORPORATED BY REFERENCE
Portions of the registrant’s definitive proxy statement for its 2026 Annual General Meeting of shareholders to be filed with the Securities and Exchange Commission within 120 days after the end of the fiscal year ended March 31, 2026 are incorporated by reference into Part III of this Annual Report on Form 10-K.
    
Amendment Flag false    
Document Fiscal Year Focus 2026    
Document Fiscal Period Focus FY    
Entity Central Index Key 0001159152