Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Stock-Based Compensation - Assumptions Used for Restricted Stock Grants (Details)

v3.21.1
Stock-Based Compensation - Assumptions Used for Restricted Stock Grants (Details) - Restricted Stock Units (Market Condition)
12 Months Ended
Mar. 31, 2021
$ / shares
shares
September 2020 Grant  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Dividend yield (per annum) 0.00%
Expected volatility 39.20%
Risk free interest rate 0.20%
Expected life in years 2 years 10 months 24 days
JHX stock price at grant date (A$ per share) | $ / shares $ 30.33
Number of restricted stock units (in shares) | shares 167,491
November 2020 Grant  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Dividend yield (per annum) 1.30%
Expected volatility 40.10%
Risk free interest rate 0.20%
Expected life in years 2 years 9 months 18 days
JHX stock price at grant date (A$ per share) | $ / shares $ 37.24
Number of restricted stock units (in shares) | shares 127,083
February 2020 Grant  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Dividend yield (per annum) 2.90%
Expected volatility 26.60%
Risk free interest rate 1.20%
Expected life in years 2 years 6 months
JHX stock price at grant date (A$ per share) | $ / shares $ 29.54
Number of restricted stock units (in shares) | shares 6,676
September 2019 Grant  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Dividend yield (per annum) 3.10%
Expected volatility 26.60%
Risk free interest rate 1.60%
Expected life in years 2 years 10 months 24 days
JHX stock price at grant date (A$ per share) | $ / shares $ 24.69
Number of restricted stock units (in shares) | shares 477,979
August 2019 Grant  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Dividend yield (per annum) 3.10%
Expected volatility 27.80%
Risk free interest rate 1.60%
Expected life in years 2 years
JHX stock price at grant date (A$ per share) | $ / shares $ 21.68
Number of restricted stock units (in shares) | shares 18,518