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

Stock-Based Compensation - Additional Information (Detail)

v3.19.1
Stock-Based Compensation - Additional Information (Detail)
12 Months Ended
Sep. 17, 2018
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Aug. 17, 2018
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Sep. 18, 2017
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Aug. 21, 2017
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Sep. 16, 2015
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Sep. 16, 2014
shares
Mar. 31, 2019
USD ($)
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Mar. 31, 2019
AUD ($)
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Mar. 31, 2018
USD ($)
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Mar. 31, 2018
AUD ($)
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Mar. 31, 2017
USD ($)
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Unrecognized compensation cost related to stock-based compensation cost | $             $ 18,300,000        
Estimated weighted average amortization, period of recognition             2 years 2 months 24 days 2 years 2 months 24 days      
Restricted stock units outstanding (in shares)             4,261,508   4,137,592 4,137,592 3,340,245
Intrinsic value of stock options exercised | $               $ 0   $ 800,000  
Excess tax benefits from share-based awards | $             $ 0   $ 0   $ 3,000,000
Restricted stock units granted (in shares)             1,714,094 1,714,094 1,779,904 1,779,904  
Restricted stock units vested (in shares)             745,787 745,787 615,334 615,334  
Unvested restricted stock units cancelled (in shares)             844,391 844,391 367,223 367,223  
Scorecard LTI - cash settled units granted under the terms of LTIP (in shares)   1,073,396   1,545,750              
Average closing price period             20 days 20 days      
Restricted Stock Units Service Vesting [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Restricted stock units granted (in shares)             617,793 617,793 332,262 332,262  
Restricted stock units vested (in shares)             242,964 242,964 237,480 237,480  
Restricted Stock Units Performance Vesting [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
LTI units granted (in shares)   357,797   515,249              
Restricted stock units vested (in shares)             284,350 284,350      
Unvested restricted stock units cancelled (in shares) 199,162                    
Restricted Stock Units (Market Condition) [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Restricted stock units granted (in shares)   663,738   932,393              
Restricted stock units vested (in shares)             218,473 218,473 156,812 156,812  
Long Term Incentive Award [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
LTI units granted (in shares)   153,667 197,800   456,995 454,179          
2001 Plan [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Issue of shares authorized (in shares)             45,077,100        
Percentage of grants exercised after first year (as percent)             25.00% 25.00%      
Percentage of grants exercised after second year (as percent)             25.00% 25.00%      
Percentage of grants exercised after third year (as percent)             50.00% 50.00%      
Restricted stock units outstanding (in shares)             910,386        
Long-Term Incentive Plan 2006 [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Restricted stock units outstanding (in shares)             4,261,508        
LTI units granted (in shares)             13,571,439 13,571,439