Investments in Marketable Securities - Summary of Investments in Marketable Securities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Mar. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	$ 1,331	$ 726
Available-for-sale debt securities, Unrealized gains	33	24
Available-for-sale debt securities, Unrealized losses	(10)	(14)
Available-for-sale debt securities, Fair value	1,354	736
Equity investments, Fair value	3,481	4,084
Investments in marketable securities total	4,835	4,820
U.S. government and agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	448	217
Available-for-sale debt securities, Unrealized gains	5	4
Available-for-sale debt securities, Unrealized losses	(8)	(10)
Available-for-sale debt securities, Fair value	445	211
Foreign government and agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	33
Available-for-sale debt securities, Unrealized gains	0
Available-for-sale debt securities, Unrealized losses	0
Available-for-sale debt securities, Fair value	33
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	2	2
Available-for-sale debt securities, Unrealized losses	0	0
Available-for-sale debt securities, Fair value	11	10
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	8	196
Available-for-sale debt securities, Unrealized gains	0	0
Available-for-sale debt securities, Unrealized losses	0	0
Available-for-sale debt securities, Fair value	8	196
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	638	177
Available-for-sale debt securities, Unrealized gains	19	12
Available-for-sale debt securities, Unrealized losses	(1)	(2)
Available-for-sale debt securities, Fair value	656	187
U.S. government agency mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	24	31
Available-for-sale debt securities, Unrealized gains	1	1
Available-for-sale debt securities, Unrealized losses	0	0
Available-for-sale debt securities, Fair value	25	32
Non-agency residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	12	1
Available-for-sale debt securities, Unrealized gains	0	0
Available-for-sale debt securities, Unrealized losses	0	0
Available-for-sale debt securities, Fair value	12	1
Non-agency commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	71	47
Available-for-sale debt securities, Unrealized gains	3	2
Available-for-sale debt securities, Unrealized losses	(1)	(2)
Available-for-sale debt securities, Fair value	73	47
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Amortized cost	88	49
Available-for-sale debt securities, Unrealized gains	3	3
Available-for-sale debt securities, Unrealized losses	0	0
Available-for-sale debt securities, Fair value	$ 91	$ 52

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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