Goodwill, Spectrum License Transactions and Other Intangible Assets - Schedule of Fair Value of Intangible Assets Acquired in Merger (Details) - USD ($) $ in Millions		12 Months Ended
Apr. 01, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Fixed period		15 years
Sprint
Finite-Lived Intangible Assets [Line Items]
Total intangible assets acquired	$ 51,725
Sprint \| Tradenames
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	2 years
Finite-lived, Fair Value (in millions)	$ 207
Sprint \| Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	8 years
Finite-lived, Fair Value (in millions)	$ 4,900
Sprint \| Favorable spectrum leases
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	18 years
Finite-lived, Fair Value (in millions)	$ 790
Sprint \| Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	7 years
Finite-lived, Fair Value (in millions)	$ 428
Sprint \| Favorable lease (asset)
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	18 years
Finite-lived, Fair Value (in millions)	$ 790
Sprint \| Unfavorable spectrum leases
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	19 years
Finite-lived, Fair Value (in millions)	$ 197
Sprint \| Spectrum Licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived, Fair Value (in millions)	$ 45,400
Fixed period	15 years

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