Products and Services Revenues (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) category	Sep. 30, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Number of categories of products and services | category			5
Disaggregation of Revenue [Line Items]
Operating revenues	$ 1,971	$ 1,952	$ 5,935	$ 5,828
IP and Data Services
Disaggregation of Revenue [Line Items]
Operating revenues	889	910	2,687	2,748
Transport and Infrastructure
Disaggregation of Revenue [Line Items]
Operating revenues	654	636	1,936	1,897
Voice and Collaboration
Disaggregation of Revenue [Line Items]
Operating revenues	350	362	1,085	1,043
Other
Disaggregation of Revenue [Line Items]
Operating revenues	25	3	74	6
Affiliate Services
Disaggregation of Revenue [Line Items]
Operating revenues	$ 53	$ 41	$ 153	$ 134