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Share-Based Compensation (Details Textual) - USD ($)	12 Months Ended
Share-Based Compensation (Details Textual) - USD ($)	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Share-based Compensation by Award [Line Items]
Award vesting percentage	75.00%
Hindalco SARs [Member]
Share-based Compensation by Award [Line Items]
Total share-based liabilities paid	$ 12,000,000	$ 5,000,000	$ 8,000,000
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation by Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 4 months 24 days
Award expiration period	7 years
Stock Appreciation Rights (SARs) [Member] \| Hindalco SARs [Member]
Share-based Compensation by Award [Line Items]
Granted (shares)	1,451,753	2,620,019	2,393,378
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 7,000,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 2 months 12 days
SARs outstanding (in shares)	4,914,602	6,778,329
Restricted Stock Units (RSUs) [Member]
Share-based Compensation by Award [Line Items]
Award vesting percentage	33.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 12,000,000
Requisite service period (years)	3 years
Restricted Stock Units (RSUs) [Member] \| Hindalco RSUs [Member]
Share-based Compensation by Award [Line Items]
Total share-based liabilities paid	$ 15,000,000	$ 13,000,000	$ 15,000,000
Maximum
Share-based Compensation by Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 3
Maximum \| Stock Appreciation Rights (SARs) [Member]
Share-based Compensation by Award [Line Items]
Award vesting percentage	33.00%