Background (Details) - USD ($)		3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 01, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2020	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Book overdraft balance		$ 0		$ 0		$ 106,000,000
Lease income		$ 333,000,000	$ 205,000,000	$ 666,000,000	$ 404,000,000
Percent of operating revenue		6.00%	4.00%	6.00%	4.00%
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		$ (5,192,000,000)	$ (5,375,000,000)	$ (10,420,000,000)	$ (10,802,000,000)
Reduction to cost of services and products		(2,232,000,000)	(2,243,000,000)	(4,467,000,000)	(4,543,000,000)
Stockholders' equity		13,462,000,000	13,673,000,000	13,462,000,000	13,673,000,000	$ 13,470,000,000
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member					us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201602Member
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity		(6,109,000,000)	(7,340,000,000)	(6,109,000,000)	(7,340,000,000)	$ (6,814,000,000)	$ (1,643,000,000)	$ (6,486,000,000)	$ (7,712,000,000)
Accumulated Deficit | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity						$ 9,000,000	$ 96,000,000
Change in Accounting Principle, Universal Service Fund
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		204,000,000	203,000,000	419,000,000	423,000,000
Reduction to cost of services and products		$ 204,000,000	$ 203,000,000	$ 419,000,000	$ 423,000,000