Cash and Cash Equivalents and Investments in Marketable Securities - Schedule of Gains and Losses on Investments in Marketable Securities Presented in Our Consolidated Statement of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Available-for-sale debt securities:
Unrealized gains (losses) on securities for which the fair value option was elected	$ 9	$ (13)	$ (17)
Realized losses on sales, net	(5)	(1)	(38)
Equity investments:
Unrealized gains (losses)	142	296	(297)
Realized losses on sales, net	$ (56)	$ (137)	$ (23)