Related Party Transactions (Schedule of Related Party Transactions) (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Cost of equipment sales	$ 6,082	$ 6,109	$ 6,583
Brightstar [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties	187	188
Accounts Payable, Related Parties, Current	109	88
Revenue from Related Parties	1,890	1,922	1,682
Cost of equipment sales	$ 1,969	$ 1,986	$ 1,600

Cost of equipment sales

No definition available.

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Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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For an unclassified balance sheet, amount of receivables arising from transactions with related parties.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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