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Restructuring and Impairment - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment, net			$ 53	$ 42	$ 33
Accelerated depreciation			17
Restructuring charges			19
Non-cash restructuring and impairment charges			34	28	23
Loss on sale or disposal of assets, net			4	6	$ 1
Minimum
Restructuring Cost and Reserve [Line Items]
Expected cost	$ 50		50
Minimum \| Forecast \| Fairmont Plant
Restructuring Cost and Reserve [Line Items]
Loss on sale or disposal of assets, net		$ 35
Maximum
Restructuring Cost and Reserve [Line Items]
Expected cost	70		70
Maximum \| Forecast \| Fairmont Plant
Restructuring Cost and Reserve [Line Items]
Loss on sale or disposal of assets, net		$ 45
West Virginia
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation				16
Restructuring charges				5
Facility Closing
Restructuring Cost and Reserve [Line Items]
Non-cash restructuring and impairment charges			17
Facility Closing \| West Virginia
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 4
Employees \| Richmond Plant
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2
Other Current Liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring liabilities, short-term	$ 8		$ 8