Intangible Assets (Details) - Licenses $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Licenses
Balance, beginning of period	$ 2,223
Acquisitions	1
Transferred to Assets held for sale	(10)
Exchanges - Licenses received	18
Exchanges - Licenses surrendered	(1)
Balance, end of period	$ 2,231

The increase (decrease) during the period in book value of long-lived assets that the reporting entity plans to sell within one year (or one business cycle).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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Period Type:	duration

- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of increase in assets, excluding financial assets and goodwill, lacking physical substance with an indefinite life, from an acquisition.

+ References

No definition available.

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- Definition

Amount of assets received, excluding financial assets and goodwill, lacking physical substance with an indefinite life, from an exchange.

+ References

No definition available.

+ Details

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- Definition

Amount of assets disposed of, excluding financial assets and goodwill, lacking physical substance with an indefinite life, in an exchange.

+ References

No definition available.

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