Capital Stock - Schedule of Share-Based Compensation Expense, by Expense Category (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Share-Based Compensation Expense [Line Items]
Total share-based compensation expense	$ 57.9	$ 62.5	$ 73.4
General and administration
Share-Based Compensation Expense [Line Items]
Total share-based compensation expense	53.0	54.8	69.2
Restructuring and other
Share-Based Compensation Expense [Line Items]
Total share-based compensation expense	$ 4.9	$ 7.7	$ 4.2