| Stock-Based Compensation (Tables)
 | 12 Months Ended | 
| Mar. 31, 2023 | 
|---|
| Share-Based Payment Arrangement [Abstract] |  | 
| Schedule of Stock-Based Compensation Expense | Total stock-based compensation expense consists of the following: 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Years Ended 31 March |  
| (Millions of US dollars) | 2023 |  | 2022 |  | 2021 |  
| Liability Awards | $ | 2.7 |  |  | $ | 3.2 |  |  | $ | 21.7 |  |  
| Equity Awards | 15.7 |  |  | 9.0 |  |  | 18.0 |  |  
| Total stock-based compensation expense | $ | 18.4 |  |  | $ | 12.2 |  |  | $ | 39.7 |  |  | 
| Summary of Stock Options Available for Grant | The following table summarizes the Company’s shares available for grant as options, RSUs or other equity instruments under the LTIP and 2001 Plan: 
|  |  |  |  |  |  |  
|   | Shares Available for
 Grant
 |  
| Balance at 31 March 2021 | 22,087,623 |  |  
| Granted | (597,927) |  |  
| Balance at 31 March 2022 | 21,489,696 |  |  
| Granted | (2,540,893) |  |  
| Balance at 31 March 2023 | 18,948,803 |  |  | 
| Schedule of Stock Options Roll Forward | The following table summarizes the Company's stock options activity during the noted period: 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Outstanding Options |  
|  |  | Number of Options |  | Weighted Average Exercise Price (A$)
 |  
| Balance at 31 March 2022 |  | — |  |  | — |  |  
| Granted |  | 269,221 |  |  | 33.05 |  |  
| Balance at 31 March 2023 |  | 269,221 |  |  | 33.05 |  |  
| Options exercisable at 31 March 2023 |  | — |  |  | — |  |  | 
| Restricted Stock Unit Activity | The following table summarizes the Company’s RSU activity: 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| (Units) | Service Vesting
 (2001 Plan)
 |  | Performance Vesting
 (LTIP)
 |  | Market Conditions (LTIP)
 |  | Total |  | Weighted Average Fair
 Value at Grant
 Date (A$)
 |  
| Outstanding at 31 March 2021 | 593,486 |  |  | 726,288 |  |  | 1,286,922 |  |  | 2,606,696 |  |  | 19.01 |  |  
| Granted | 233,443 |  |  | 141,015 |  |  | 223,469 |  |  | 597,927 |  |  | 41.73 |  |  
| Vested | (313,641) |  |  | (248,202) |  |  | (565,878) |  |  | (1,127,721) |  |  | 14.96 |  |  
| Forfeited | (98,613) |  |  | (327,397) |  |  | (450,480) |  |  | (876,490) |  |  | 27.73 |  |  
| Outstanding at 31 March 2022 | 414,675 |  |  | 291,704 |  |  | 494,033 |  |  | 1,200,412 |  |  | 27.83 |  |  
| Granted | 1,279,127 |  |  | 268,009 |  |  | 724,536 |  |  | 2,271,672 |  |  | 26.12 |  |  
| Vested | (449,458) |  |  | (87,307) |  |  | (256,787) |  |  | (793,552) |  |  | 25.17 |  |  
| Forfeited | (107,818) |  |  | (100,377) |  |  | (91,738) |  |  | (299,933) |  |  | 28.46 |  |  
| Outstanding at 31 March 2023 | 1,136,526 |  |  | 372,029 |  |  | 870,044 |  |  | 2,378,599 |  |  | 26.97 |  |  | 
| Assumptions Used for Restricted Stock Grants | The following table includes the assumptions used for RSU grants (market condition) valued:  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Vesting Condition: | Market |  | Market |  | Market |  | Market |  | Market |  | Market |  | Market |  | Market |  
|  | FY23 |  | FY23 |  | FY23 |  | FY23 |  | FY23 |  | FY23 |  | FY22 |  | FY22 |  
| Date of grant | 31-Aug-22 |  | 31-Aug-22 |  | 3-Nov-22 |  | 3-Nov-22 |  | 3-Nov-22 |  | 13-Mar-23 |  | 27-Aug-21 |  | 9-Sep-21 |  
| Dividend yield (per annum) | 1.5 | % |  | 1.5 | % |  | — | % |  | — | % |  | — | % |  | — | % |  | 2.0 | % |  | 2.0 | % |  
| Expected volatility | 41.9 | % |  | 33.4 | % |  | 42.5 | % |  | 35.1 | % |  | 43.8 | % |  | 36.3 | % |  | 40.0 | % |  | 40.2 | % |  
| Risk free interest rate | 3.5 | % |  | 3.5 | % |  | 4.7 | % |  | 4.7 | % |  | 4.7 | % |  | 4.0 | % |  | 0.4 | % |  | 0.4 | % |  
| Expected life in years | 3.0 |  | 2.0 |  | 0.8 |  | 1.8 |  | 2.8 |  | 2.4 |  | 3.0 |  | 2.9 |  
| JHX stock price at grant date (A$) | 33.51 |  | 33.51 |  | 33.05 |  | 33.05 |  | 33.05 |  | 30.98 |  | 52.66 |  | 52.12 |  
| Number of restricted stock units | 387,360 |  | 102,250 |  | 38,387 |  | 39,450 |  | 115,688 |  | 41,401 |  | 130,513 |  | 92,956 |  | 
| Schedule Of Fair Value Of Restricted Stock Units Vested | 
The following table presents the total fair value of all of our restricted stock units vested:
 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Years ended 31 March |  
| (Millions of US dollars) |  | 2023 |  | 2022 |  | 2021 |  
| Total fair value vested |  | $ | 18.4 |  |  | $ | 42.6 |  |  | $ | 27.8 |  |  | 
| Cash Settled Units Activity | The following represents the activity related to the CSUs: 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | FY23 |  | FY22 |  
| Granted |  | 751,569 |  |  | 423,051 |  |  
| Vested |  | 237,600 |  |  | 433,872 |  |  
| Cancelled |  | 325,459 |  |  | 1,292,934 |  |  |