Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total Revenue	$ 1,792	$ 1,918
Adjustments for non-ASC 606 revenue	(119)	(121)
Total Revenue from Contracts with Customers	1,673	1,797
Voice and Other [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	543	590
Adjustments for non-ASC 606 revenue	(85)	(89)
Total Revenue from Contracts with Customers	458	501
Fiber Infrastructure [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	504	513
Adjustments for non-ASC 606 revenue	(31)	(31)
Total Revenue from Contracts with Customers	473	482
IP & Data Services [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	123	132
Adjustments for non-ASC 606 revenue	0	0
Total Revenue from Contracts with Customers	123	132
Affiliate Services [Member]
Disaggregation of Revenue [Line Items]
Total Revenue	622	683
Adjustments for non-ASC 606 revenue	(3)	(1)
Total Revenue from Contracts with Customers	$ 619	$ 682