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Income Taxes - Schedule of Cash Paid for Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Effective Income Tax Rate Reconciliation [Line Items]
U.S. Federal	$ 0
Foreign	5
Total income taxes paid, net of refunds received	103	$ 379	$ 336
DISTRICT OF COLUMBIA
Effective Income Tax Rate Reconciliation [Line Items]
State and local:	24
MARYLAND
Effective Income Tax Rate Reconciliation [Line Items]
State and local:	17
VIRGINIA
Effective Income Tax Rate Reconciliation [Line Items]
State and local:	37
All other states
Effective Income Tax Rate Reconciliation [Line Items]
State and local:	$ 20