Segment Information - Operating Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating revenues by products and services
Revenues	$ 5,818	$ 4,034	$ 17,665	$ 12,333
Surcharge amount on customers' bills	221	129	698	392
Business
Operating revenues by products and services
Revenues	4,285	2,425	13,033	7,485
Consumer
Operating revenues by products and services
Revenues	1,355	1,420	4,086	4,304
Operating segments
Operating revenues by products and services
Revenues	5,640	3,845	17,119	11,789
Operating segments | Business
Operating revenues by products and services
Revenues	4,285	2,425	13,033	7,485
Operating segments | Business | IP & Data Services
Operating revenues by products and services
Revenues	1,726	755	5,212	2,256
Operating segments | Business | Transport & Infrastructure
Operating revenues by products and services
Revenues	1,331	735	4,021	2,426
Operating segments | Business | Voice & Collaboration
Operating revenues by products and services
Revenues	1,075	765	3,324	2,319
Operating segments | Business | IT & Managed Services
Operating revenues by products and services
Revenues	153	170	476	484
Operating segments | Consumer
Operating revenues by products and services
Revenues	1,355	1,420	4,086	4,304
Operating segments | Consumer | IP & Data Services
Operating revenues by products and services
Revenues	70	98	249	308
Operating segments | Consumer | Transport & Infrastructure
Operating revenues by products and services
Revenues	720	697	2,171	2,063
Operating segments | Consumer | Voice & Collaboration
Operating revenues by products and services
Revenues	565	625	1,666	1,933
Corporate, Non-Segment
Operating revenues by products and services
Revenues	178	189	546	544
Corporate, Non-Segment | Regulatory Revenue
Operating revenues by products and services
Revenues	$ 178	$ 189	$ 546	$ 544