This element represents the aggregate cost of investments accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
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- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
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- Definition

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.

+ References

No definition available.

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- Definition

Reflects the sum of all other revenue and income realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

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- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606610-122999

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- Definition

Amount of cash inflow after closing and debt issuance costs received by a seller-lessee in a sale-leaseback recognized in financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 40
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-Paragraph 51
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Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Nov. 30, 2015	Oct. 31, 2014
Line of Credit [Member] \| Brightstar [Member]
Related Party Transaction [Line Items]
Line of credit facility, maximum borrowing capacity						$ 700
SoftBank [Member]
Related Party Transaction [Line Items]
Equity Method Investment, Aggregate Cost					$ 79
MLS [Member]
Related Party Transaction [Line Items]
Proceeds from sale-leaseback transaction	$ 2,200
Network Sale-Leaseback [Member]
Related Party Transaction [Line Items]
Proceeds from sale-leaseback transaction	2,200
Repayments of Debt		$ 1,900
Network Sale-Leaseback [Member] \| SoftBank [Member]
Related Party Transaction [Line Items]
Proceeds from sale-leaseback transaction	$ 250
Brightstar [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		93	$ 64	$ 102
Related Party Transaction, Other Revenues from Transactions with Related Party		154
Revenue from Related Parties		1,922	1,682	1,731
Subsidiaries [Member] \| Brightstar [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties		$ 38	$ 100	$ 103