Investments in Marketable Securities - Schedule of Continuous Unrealized Losses on Available-For-Sale Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2025	Mar. 31, 2025
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	$ 151	$ 262
Available-for-sale debt securities, 12 months or longer, Fair value	883	956
Available-for-sale debt securities, Total, Fair value	1,034	1,218
Available-for-sale debt securities, Less than 12 months, Unrealized losses	(1)	(3)
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(123)	(136)
Available-for-sale debt securities, Total, Unrealized losses	(124)	(139)
U.S. government and agency obligations [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	111	104
Available-for-sale debt securities, 12 months or longer, Fair value	513	534
Available-for-sale debt securities, Total, Fair value	624	638
Available-for-sale debt securities, Less than 12 months, Unrealized losses	0	(1)
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(81)	(82)
Available-for-sale debt securities, Total, Unrealized losses	(81)	(83)
Foreign government and agency obligations [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	2	7
Available-for-sale debt securities, 12 months or longer, Fair value	5	6
Available-for-sale debt securities, Total, Fair value	7	13
Available-for-sale debt securities, Less than 12 months, Unrealized losses	0	0
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(1)	(1)
Available-for-sale debt securities, Total, Unrealized losses	(1)	(1)
Municipal debt securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	0	0
Available-for-sale debt securities, 12 months or longer, Fair value	2	2
Available-for-sale debt securities, Total, Fair value	2	2
Available-for-sale debt securities, Less than 12 months, Unrealized losses	0	0
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(1)	(1)
Available-for-sale debt securities, Total, Unrealized losses	(1)	(1)
Corporate debt securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	24	42
Available-for-sale debt securities, 12 months or longer, Fair value	245	288
Available-for-sale debt securities, Total, Fair value	269	330
Available-for-sale debt securities, Less than 12 months, Unrealized losses	(1)	(1)
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(29)	(39)
Available-for-sale debt securities, Total, Unrealized losses	(30)	(40)
U.S. government agency mortgage-backed securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	6	68
Available-for-sale debt securities, 12 months or longer, Fair value	37	37
Available-for-sale debt securities, Total, Fair value	43	105
Available-for-sale debt securities, Less than 12 months, Unrealized losses	0	(1)
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(3)	(4)
Available-for-sale debt securities, Total, Unrealized losses	(3)	(5)
Non-agency residential mortgage-backed securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	0	1
Available-for-sale debt securities, 12 months or longer, Fair value	7	7
Available-for-sale debt securities, Total, Fair value	7	8
Available-for-sale debt securities, Less than 12 months, Unrealized losses	0	0
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(1)	(1)
Available-for-sale debt securities, Total, Unrealized losses	(1)	(1)
Non-agency commercial mortgage-backed securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	1	3
Available-for-sale debt securities, 12 months or longer, Fair value	42	41
Available-for-sale debt securities, Total, Fair value	43	44
Available-for-sale debt securities, Less than 12 months, Unrealized losses	0	0
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(5)	(5)
Available-for-sale debt securities, Total, Unrealized losses	(5)	(5)
Asset-backed securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale debt securities, Less than 12 months, Fair value	7	37
Available-for-sale debt securities, 12 months or longer, Fair value	32	41
Available-for-sale debt securities, Total, Fair value	39	78
Available-for-sale debt securities, Less than 12 months, Unrealized losses	0	0
Available-for-sale debt securities, 12 months or longer, Unrealized losses	(2)	(3)
Available-for-sale debt securities, Total, Unrealized losses	$ (2)	$ (3)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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