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

Capital Management and Dividends - Additional Information (Detail)

v3.7.0.1
Capital Management and Dividends - Additional Information (Detail)
AUD / shares in Units, $ / shares in Units, AUD in Millions, $ in Millions
 3 Months Ended 12 Months Ended
May 18, 2017
$ / shares
Mar. 31, 2017
Sep. 30, 2016
USD ($)
$ / shares
shares
Sep. 30, 2016
AUD
AUD / shares
shares
Mar. 31, 2017
USD ($)
Mar. 31, 2016
USD ($)
Mar. 31, 2015
USD ($)
Dividends Payable [Line Items]              
Aggregate cost of common stock repurchased | $         $ 99.8 $ 22.3 $ 9.1
Ordinary dividend record date   Jun. 08, 2017          
Ordinary dividend payment Date   Aug. 04, 2017          
Subsequent Event [Member]              
Dividends Payable [Line Items]              
Ordinary dividend declared | $ / shares $ 28.0            
Fiscal 2017 Program [Member]              
Dividends Payable [Line Items]              
Aggregate cost of common stock repurchased     $ 99.8 AUD 131.4 $ 100.0    
Aggregate number of common stock repurchased and cancelled | shares     6,090,133 6,090,133      
Average price paid per share of common stock repurchased and cancelled | (per share)     $ 16.40 AUD 21.58