Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions		1 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Feb. 28, 2018	Jun. 30, 2018
Operating Leased Assets [Line Items]
Operating leases, due 2019	$ 2,500	$ 2,500		$ 2,500
Operating leases, total due 2020 and 2021	4,300	4,300		4,300
Operating leases, total dude 2022 and 2023	2,800	2,800		2,800
Operating leases total due thereafter	2,800	2,800		2,800
Purchase obligation, due 2019	2,200	2,200		2,200
Purchase obligation, due 2020 and 2021	2,500	2,500		2,500
Purchase obligation, Due 2022 and 2023	1,600	1,600		1,600
Purchase obligation total due thereafter	1,100	1,100		$ 1,100
Corporate Headquarters Facility
Operating Leased Assets [Line Items]
Increase in minimum lease payments			$ 400
Tower Obligations
Operating Leased Assets [Line Items]
Increase in minimum lease payments			$ 385
Minimum | Network Equipment
Operating Leased Assets [Line Items]
Network equipment purchase agreement	$ 175
Maximum | Network Equipment
Operating Leased Assets [Line Items]
Network equipment purchase agreement		$ 3,500
Cell Sites | Minimum
Operating Leased Assets [Line Items]
Initial non-cancelable term				5 years
Cell Sites | Maximum
Operating Leased Assets [Line Items]
Initial non-cancelable term				10 years