Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Land	$ 41	$ 37
Buildings	281	281
Leasehold and land improvements	1,570	1,504
Cell site equipment	4,381	4,247
Switching equipment	1,090	1,115
Office furniture and equipment	193	209
Other operating assets and equipment	47	47
System development	1,790	1,676
Work in process	167	218
Total property, plant and equipment, gross	9,560	9,334
Accumulated depreciation and amortization	(6,984)	(6,710)
Property, plant and equipment, net	2,576	2,624
Depreciation and amortization expense	$ 637	$ 682	$ 662
Buildings
Property, Plant and Equipment [Line Items]
Useful life	20 years
Leasehold and land improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful life	1 year
Leasehold and land improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful life	30 years
Cell site equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	7 years
Cell site equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	30 years
Switching equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Switching equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	8 years
Office furniture and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Office furniture and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Other operating assets and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Other operating assets and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	5 years
System development | Minimum
Property, Plant and Equipment [Line Items]
Useful life	1 year
System development | Maximum
Property, Plant and Equipment [Line Items]
Useful life	7 years