v3.26.1
Earnings per Share - Summary of Group's Basic And Diluted Net Income/(loss) Per Ordinary Share (Detail) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Earnings Per Share [Abstract]      
Net income $ 498.7 $ 550.3 $ 501.5
Weighted average number of shares – basic (in millions of shares) 1,019.5 1,032.3 1,032.6
Plus the effect of dilution from share awards (in millions of shares) 10.2 13.4 16.3
Weighted average number of shares – diluted (in millions of shares) 1,029.7 1,045.7 1,048.9
Earnings per share: Basic (cents) $ 48.92 $ 53.31 $ 48.57
Earnings per share: Diluted (cents) $ 48.43 $ 52.63 $ 47.81