Property and Equipment (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($) tower_site	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (33,118)	$ (33,118)	$ (33,118)	$ (31,297)
Property and equipment, net	$ 21,984	21,984	21,984	23,359		$ 21,020
Capitalized interest			473	362	$ 136
Number of wireless communications tower sites sold | tower_site	168
Proceeds from sales of tower sites	$ 38		$ 38	0	0
Gain recognized as a reduction in Cost of services, exclusive of depreciation and amortization		13
Initial term of space leased out			10 years
Depreciation expense			$ 6,000	6,400	5,800
Depreciation expense for lease devices			543	940	$ 1,000
Buildings and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	2,587	2,587	2,587	2,428
Wireless communications systems
Property, Plant and Equipment [Line Items]
Property, plant and equipment	34,353	34,353	34,353	35,282
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,345	1,345	1,345	1,299
Capitalized software
Property, Plant and Equipment [Line Items]
Property, plant and equipment	12,705	12,705	12,705	11,712
Leased wireless devices
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,139	1,139	1,139	1,159
Accumulated depreciation and amortization	(407)	(407)	(407)
Property and equipment, net	732	732	732
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 2,973	$ 2,973	$ 2,973	$ 2,776
Maximum | Buildings and equipment
Property, Plant and Equipment [Line Items]
Useful life (in years)			40 years
Maximum | Wireless communications systems
Property, Plant and Equipment [Line Items]
Useful life (in years)			20 years
Maximum | Leasehold improvements
Property, Plant and Equipment [Line Items]
Useful life (in years)			12 years
Maximum | Capitalized software
Property, Plant and Equipment [Line Items]
Useful life (in years)			10 years
Maximum | Leased wireless devices
Property, Plant and Equipment [Line Items]
Useful life (in years)			18 months