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

Stock-Based Compensation - Additional Information (Detail)

v3.7.0.1
Stock-Based Compensation - Additional Information (Detail)
AUD / shares in Units, AUD in Millions, $ in Millions
12 Months Ended
Sep. 16, 2016
shares
Sep. 16, 2015
shares
Sep. 14, 2015
shares
Mar. 31, 2017
USD ($)
shares
Mar. 31, 2017
AUD
AUD / shares
shares
Mar. 31, 2016
USD ($)
shares
Mar. 31, 2016
AUD
shares
Mar. 31, 2015
USD ($)
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unrecognized compensation cost related to stock-based compensation cost | $       $ 15.0        
Estimated weighted average amortization, period of recognition       1 year 7 months 6 days 1 year 7 months 6 days      
Issue of shares authorized           5,000,000 5,000,000  
Restricted stock units granted       1,179,994 1,179,994 1,410,560 1,410,560  
Restricted stock units outstanding       3,340,245   4,049,454 4,049,454 4,008,001
Intrinsic value of stock options exercised | AUD         AUD 0.8   AUD 2.9  
Excess tax benefits from share-based awards | $       $ 3.0   $ 0.4   $ 1.4
Closing stock price | AUD / shares         AUD 20.57      
Restricted stock units vested       1,314,825 1,314,825 1,219,352 1,219,352  
Unvested restricted stock units cancelled       574,378 574,378 149,755 149,755  
Scorecard LTI - cash settled units granted under the terms of LTIP 458,484 566,936            
Average closing price period 20 days 20 days            
Restricted Stock Units Performance Vesting [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
LTI units granted 407,539 503,944            
Restricted stock units vested       281,468 281,468      
Restricted stock unit deferred vesting period   3 years            
Unvested restricted stock units cancelled 152,611              
Restricted Stock Units Service Vesting [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Restricted stock units granted       315,636 315,636 327,354 327,354  
Restricted stock units vested       304,470 304,470 228,481 228,481  
Restricted Stock Units (Market Condition) [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Restricted stock units granted 456,819 579,262            
Restricted stock units vested       728,887 728,887 659,725 659,725  
Long Term Incentive Award [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
LTI units granted 316,841   288,552          
Long Term Incentive Award [Member] | Maximum [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
LTI units granted 518,647   506,627          
Long Term Incentive Award [Member] | Maximum [Member] | James Hardie Industries Plc [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Average closing price period 20 days   20 days          
Long-Term Incentive Plan 2006 [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Restricted stock units outstanding       2,720,664        
LTI units granted       11,027,496 11,027,496      
2001 Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Issue of shares authorized       45,077,100        
Percentage of grants exercised after first year       25.00% 25.00%      
Percentage of grants exercised after second year       25.00% 25.00%      
Percentage of grants exercised after third year       50.00% 50.00%      
Unexercised grants expiration year       10 years 10 years      
Unexercised grants expiration days       90 days 90 days      
Restricted stock units granted       315,636 315,636 327,354 327,354  
Restricted stock units outstanding       619,581