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

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

v3.8.0.1
Stock-Based Compensation - Assumptions Used for Restricted Stock Grants (Detail) - Restricted Stock Units (Market Condition) [Member] - $ / shares
12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Date of grant Aug. 21, 2017 Sep. 16, 2016
Dividend yield (per annum) 3.00% 2.30%
Expected volatility 30.10% 31.50%
Risk free interest rate 1.50% 1.10%
Expected life in years 3 years 3 months 24 days 3 years
JHX stock price at grant date (A$ per share)) $ 17.91 $ 20.82
Number of restricted stock units (in shares) 932,393 456,819