Investments in Marketable Securities - Summary of Contractual Maturities of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions		Jun. 30, 2021	Mar. 31, 2021
Available-for-sale debt securities, Amortized cost
Due within 1 Year, Amortized cost		$ 147
Due after 1 Year through 5 Years, Amortized cost		467
Due after 5 Years through 10 Years, Amortized cost		316
Due after 10 Years, Amortized cost		224
Mortgage-backed and asset-backed securities, Amortized cost	[1]	187
Available-for-sale debt securities, Amortized cost		$ 1,341	$ 726
Debt Securities, Available-for-sale, Maturity Allocation [Extensible List]		us-gaap:DebtSecuritiesMaturityAllocationContractualMaturityMember
Available-for-sale debt securities, Fair value
Due within 1 Year, Fair value		$ 149
Due after 1 Year through 5 Years, Fair value		476
Due after 5 Years through 10 Years, Fair value		321
Due after 10 Years, Fair value		232
Mortgage-backed and asset-backed securities, Fair value	[1]	194
Total, Fair value		$ 1,372	$ 736
Debt Securities, Available-for-sale, Maturity Allocation [Extensible List]		us-gaap:DebtSecuritiesMaturityAllocationContractualMaturityMember

[1] Mortgage-backed and asset-backed securities are shown separately from other maturity groupings as these securities have multiple maturity dates.