Receivables - Receivables, Net of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables, net of allowance for doubtful accounts	$ 4,156	$ 4,392
Billed trade receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables, net of allowance for doubtful accounts	2,009	2,094
Unbilled receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables, net of allowance for doubtful accounts	1,214	1,419
Other receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables, net of allowance for doubtful accounts	$ 933	$ 879