Segment Information (Details 2) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) category	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Operating revenues by products and services
Number of categories of products and services (categories) | category									5
Operating revenue	$ 5,778	$ 5,818	$ 5,902	$ 5,945	$ 5,323	$ 4,034	$ 4,090	$ 4,209	$ 23,443	$ 17,656	$ 17,470
Surcharge amount on customers' bills									952	601	572
Business
Operating revenues by products and services
Operating revenue									17,349	11,220	10,704
Consumer
Operating revenues by products and services
Operating revenue									5,371	5,704	6,062
Operating Segments | Business
Operating revenues by products and services
Operating revenue									17,349	11,220	10,704
Operating Segments | Business | IP & Data Services
Operating revenues by products and services
Operating revenue									6,971	3,682	2,957
Operating Segments | Business | Transport & Infrastructure
Operating revenues by products and services
Operating revenue									5,356	3,569	3,807
Operating Segments | Business | Voice & Collaboration
Operating revenues by products and services
Operating revenue									4,401	3,317	3,299
Operating Segments | Business | IT & Managed Services
Operating revenues by products and services
Operating revenue									621	652	641
Operating Segments | Consumer
Operating revenues by products and services
Operating revenue									5,371	5,704	6,062
Operating Segments | Consumer | IP & Data Services
Operating revenues by products and services
Operating revenue									308	401	461
Operating Segments | Consumer | Transport & Infrastructure
Operating revenues by products and services
Operating revenue									2,892	2,776	2,776
Operating Segments | Consumer | Voice & Collaboration
Operating revenues by products and services
Operating revenue									2,171	2,527	2,825
Corporate, Non-Segment
Operating revenues by products and services
Operating revenue									723	732	704
Corporate, Non-Segment | Regulatory Revenue
Operating revenues by products and services
Operating revenue									$ 723	$ 732	$ 704