Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Total Revenue	$ 1,724	$ 1,799	$ 3,516	$ 3,717
Adjustments for non-ASC 606 revenue	(118)	(121)	(237)	(242)
Total Revenue from Contracts with Customers	$ 1,606	$ 1,678	$ 3,279	$ 3,475
Percent of operating revenue	5.00%	4.00%	4.00%	4.00%
Voice and Other [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	$ 530	$ 569	$ 1,073	$ 1,159
Adjustments for non-ASC 606 revenue	(83)	(87)	(168)	(176)
Total Revenue from Contracts with Customers	447	482	905	983
Fiber Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	501	509	1,005	1,022
Adjustments for non-ASC 606 revenue	(29)	(33)	(60)	(64)
Total Revenue from Contracts with Customers	472	476	945	958
IP & Data Services [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	116	129	239	261
Adjustments for non-ASC 606 revenue	0	0	0	0
Total Revenue from Contracts with Customers	116	129	239	261
Affiliate Services [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	577	592	1,199	1,275
Adjustments for non-ASC 606 revenue	(6)	(1)	(9)	(2)
Total Revenue from Contracts with Customers	$ 571	$ 591	$ 1,190	$ 1,273