Investments in Marketable Securities - Summary of Investments in Marketable Securities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Mar. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	$ 1,596	$ 1,584
Available-for-sale debt securities, Unrealized gains	1	10
Available-for-sale debt securities, Unrealized losses	(220)	(140)
Available-for-sale debt securities, Fair value	1,377	1,454
Equity investments, Fair value	3,510	3,583
Investments in marketable securities total	4,887	5,037
U.S. government and agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	792	796
Available-for-sale debt securities, Unrealized gains	0	7
Available-for-sale debt securities, Unrealized losses	(117)	(59)
Available-for-sale debt securities, Fair value	675	744
Foreign government and agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	11	14
Available-for-sale debt securities, Unrealized gains	0	0
Available-for-sale debt securities, Unrealized losses	(2)	(2)
Available-for-sale debt securities, Fair value	9	12
Municipal debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	9	8
Available-for-sale debt securities, Unrealized gains	0	1
Available-for-sale debt securities, Unrealized losses	(1)	(1)
Available-for-sale debt securities, Fair value	8	8
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	465	487
Available-for-sale debt securities, Unrealized gains	1	2
Available-for-sale debt securities, Unrealized losses	(72)	(59)
Available-for-sale debt securities, Fair value	394	430
U.S. government agency mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	122	76
Available-for-sale debt securities, Unrealized gains	0	0
Available-for-sale debt securities, Unrealized losses	(9)	(3)
Available-for-sale debt securities, Fair value	113	73
Non-agency residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	9	10
Available-for-sale debt securities, Unrealized gains	0	0
Available-for-sale debt securities, Unrealized losses	(2)	(1)
Available-for-sale debt securities, Fair value	7	9
Non-agency commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	65	66
Available-for-sale debt securities, Unrealized gains	0	0
Available-for-sale debt securities, Unrealized losses	(10)	(8)
Available-for-sale debt securities, Fair value	55	58
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	123	127
Available-for-sale debt securities, Unrealized gains	0	0
Available-for-sale debt securities, Unrealized losses	(7)	(7)
Available-for-sale debt securities, Fair value	$ 116	$ 120

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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