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Indefinite-lived Intangible Assets, Costs to Clear Assets

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Number of Licenses Acquired

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Payments to Acquire Intangible Assets, Remaining Payment Required

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Fair value at acquisition-date of the assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interests issued by the acquirer, including but not limited to, instruments or interests issued or issuable in consideration for the business combination.

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Percentage of equity in the acquiree held by the acquirer immediately before the acquisition date in a business combination.

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Carrying value of amounts transferred to third parties for security purposes that are expected to be returned or applied towards payment within one year or during the operating cycle, if shorter.

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Amount of gain (loss) on sale or disposal of intangible assets.

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

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

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Amount of divestiture of an asset lacking physical substance and having a projected indefinite period of benefit to fair value. Excludes financial assets and goodwill.

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

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The cash outflow to acquire asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

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Goodwill, Spectrum License Transactions and Other Intangible Assets - Spectrum Licenses (Details) $ in Millions		1 Months Ended					3 Months Ended				12 Months Ended
	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	May 31, 2017 USD ($)	Apr. 30, 2017 USD ($) license	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)
Indefinite-lived Intangible Assets [Roll Forward]
Purchase of spectrum licenses											$ 127	$ 5,828	$ 3,968
Gains or losses recognized on spectrum license purchase							$ 168	$ 29	$ 1	$ 37	0	235	835
Number of licenses \| license					1,525
Iowa Wireless
Indefinite-lived Intangible Assets [Roll Forward]
Spectrum licenses	$ 87										87
Unconsolidated subsidiary ownership percentage	54.00%		54.00%					54.00%
Purchase price of unconsolidated subsidiary	$ 25
Licensing Agreements
Indefinite-lived Intangible Assets [Roll Forward]
Beginning balance	$ 35,366									$ 27,014	35,366	27,014
Spectrum license acquisitions											138	8,599
Spectrum licenses transferred to held for sale											(1)	(271)
Costs to clear spectrum											56	24
Ending balance		$ 35,366					$ 35,366				35,559	$ 35,366	$ 27,014
Purchase of spectrum licenses					$ 8,000						$ 50
Gains or losses recognized on spectrum license purchase		168	$ 29			$ 37
Asset purchase deposit														$ 2,200
Remaining purchase price				$ 5,800
Licensing Agreements \| Fair Value
Indefinite-lived Intangible Assets [Roll Forward]
Spectrum license acquisitions		$ 352	$ 115			$ 123