Property, Plant, and Equipment - Schedule (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 12,009	$ 13,336
Accumulated depreciation	(2,998)	(2,818)
Net property, plant and equipment	9,011	10,518
Land
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	305	320
Fiber, conduit and other outside plant
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	5,495	6,186
Central office and other network electronics
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	3,185	3,388
Support assets
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	2,480	2,722
Construction in progress
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 544	$ 720