Goodwill, Spectrum License Transactions and Other Intangible Assets - Other Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment	$ 0	$ 0
Indefinite-lived intangible asset impairment	0	0
Finite-Lived Intangible Assets, Gross	1,527,000,000	1,565,000,000
Finite-Lived Intangible Assets, Accumulated Amortization	(1,412,000,000)	(1,367,000,000)
Net Amount	115,000,000	198,000,000		$ 186,000,000
Amortization expense for intangible assets	82,000,000	124,000,000	$ 163,000,000
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2020	83,000,000
2021	14,000,000
2022	3,000,000
2023	3,000,000
2024	3,000,000
Thereafter	9,000,000
Net Amount	115,000,000	198,000,000		$ 186,000,000
Customer lists
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	1,104,000,000	1,104,000,000
Finite-Lived Intangible Assets, Accumulated Amortization	(1,104,000,000)	(1,086,000,000)
Net Amount	0	18,000,000
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Net Amount	$ 0	18,000,000
Customer lists | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life (in years)	6 years
Trademarks and patents
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 323,000,000	312,000,000
Finite-Lived Intangible Assets, Accumulated Amortization	(258,000,000)	(225,000,000)
Net Amount	65,000,000	87,000,000
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Net Amount	$ 65,000,000	87,000,000
Trademarks and patents | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life (in years)	19 years
Other
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 100,000,000	149,000,000
Finite-Lived Intangible Assets, Accumulated Amortization	(50,000,000)	(56,000,000)
Net Amount	50,000,000	93,000,000
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Net Amount	$ 50,000,000	$ 93,000,000
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life (in years)	28 years