Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,990	$ 1,971	$ 5,964	$ 5,935
Adjustments for non-ASC 606 revenue	(241)	(234)	(719)	(687)
Total revenue from contracts with customers	1,749	1,737	5,245	5,248
Compute and Application Services
Disaggregation of Revenue [Line Items]
Total revenues	287	274	850	814
Adjustments for non-ASC 606 revenue	(126)	(124)	(380)	(371)
Total revenue from contracts with customers	161	150	470	443
IP and Data Services
Disaggregation of Revenue [Line Items]
Total revenues	890	878	2,659	2,639
Adjustments for non-ASC 606 revenue	0	0	0	0
Total revenue from contracts with customers	890	878	2,659	2,639
Fiber Infrastructure Services
Disaggregation of Revenue [Line Items]
Total revenues	412	379	1,210	1,116
Adjustments for non-ASC 606 revenue	(56)	(55)	(164)	(157)
Total revenue from contracts with customers	356	324	1,046	959
Voice and Other
Disaggregation of Revenue [Line Items]
Total revenues	345	387	1,078	1,213
Adjustments for non-ASC 606 revenue	(3)	(2)	(8)	(6)
Total revenue from contracts with customers	342	385	1,070	1,207
Affiliate Services
Disaggregation of Revenue [Line Items]
Total revenues	56	53	167	153
Adjustments for non-ASC 606 revenue	(56)	(53)	(167)	(153)
Total revenue from contracts with customers	$ 0	$ 0	$ 0	$ 0