v3.25.1
Segment, Geographical Area, Major Customer and Major Supplier Information (Purchases - RTA) (Details)
12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Cost of Goods Sold | Supplier Concentration Risk | Rio Tinto Alcan      
Revenue, Major Customer [Line Items]      
Purchases from Rio Tinto as a percentage of total combined metal purchases 9.00% 9.00% 8.00%