Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue	$ 5,570	$ 5,606	$ 5,578	$ 5,647	$ 5,778	$ 5,818	$ 5,902	$ 5,945	$ 22,401	$ 23,443	$ 17,656
Adjustments									(1,953)	(1,538)
Total Revenue from Contracts with Customers									20,448	21,905
Goods and services transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue from Contracts with Customers									221	230
Services performed over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue from Contracts with Customers									20,227	21,675
IP and Data Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									7,000	6,961	3,594
Transport and Infrastructure
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									5,203	5,433	3,663
Voice and Collaboration
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									4,021	4,309	3,304
IT and Managed Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									535	624	644
Broadband
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									2,876	2,822	2,698
Voice
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,881	2,173	2,531
Other
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									251	392	491
Operating Segments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									22,401	23,443	17,463
Operating Segments | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									3,596	3,653	1,382
Adjustments									(365)	(83)
Total Revenue from Contracts with Customers									3,231	3,570
Operating Segments | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									6,133	6,133	4,186
Adjustments									(134)	(43)
Total Revenue from Contracts with Customers									5,999	6,090
Operating Segments | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									2,956	3,144	2,418
Adjustments									(36)	(40)
Total Revenue from Contracts with Customers									2,920	3,104
Operating Segments | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									4,074	4,397	3,026
Adjustments									(545)	(397)
Total Revenue from Contracts with Customers									3,529	4,000
Operating Segments | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									5,642	6,116	6,451
Adjustments									(873)	(975)
Total Revenue from Contracts with Customers									4,769	5,141
Operating Segments | IP and Data Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									7,000	6,961	3,593
Operating Segments | IP and Data Services | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,676	1,728	528
Adjustments									0	0
Total Revenue from Contracts with Customers									1,676	1,728
Operating Segments | IP and Data Services | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									2,763	2,673	1,515
Adjustments									0	0
Total Revenue from Contracts with Customers									2,763	2,673
Operating Segments | IP and Data Services | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,184	1,178	634
Adjustments									0	0
Total Revenue from Contracts with Customers									1,184	1,178
Operating Segments | IP and Data Services | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,377	1,382	916
Adjustments									0	0
Total Revenue from Contracts with Customers									1,377	1,382
Operating Segments | IP and Data Services | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Transport and Infrastructure
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									5,203	5,433	3,471
Operating Segments | Transport and Infrastructure | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,318	1,276	406
Adjustments									(365)	(83)
Total Revenue from Contracts with Customers									953	1,193
Operating Segments | Transport and Infrastructure | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,545	1,550	1,116
Adjustments									(134)	(43)
Total Revenue from Contracts with Customers									1,411	1,507
Operating Segments | Transport and Infrastructure | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									420	471	419
Adjustments									(36)	(40)
Total Revenue from Contracts with Customers									384	431
Operating Segments | Transport and Infrastructure | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,920	2,136	1,530
Adjustments									(545)	(397)
Total Revenue from Contracts with Customers									1,375	1,739
Operating Segments | Transport and Infrastructure | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Voice and Collaboration
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									4,021	4,309	3,304
Operating Segments | Voice and Collaboration | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									377	387	176
Adjustments									0	0
Total Revenue from Contracts with Customers									377	387
Operating Segments | Voice and Collaboration | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,567	1,607	1,245
Adjustments									0	0
Total Revenue from Contracts with Customers									1,567	1,607
Operating Segments | Voice and Collaboration | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,306	1,443	1,314
Adjustments									0	0
Total Revenue from Contracts with Customers									1,306	1,443
Operating Segments | Voice and Collaboration | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									771	872	569
Adjustments									0	0
Total Revenue from Contracts with Customers									771	872
Operating Segments | Voice and Collaboration | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | IT and Managed Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									535	624	644
Operating Segments | IT and Managed Services | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									225	262	272
Adjustments									0	0
Total Revenue from Contracts with Customers									225	262
Operating Segments | IT and Managed Services | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									258	303	310
Adjustments									0	0
Total Revenue from Contracts with Customers									258	303
Operating Segments | IT and Managed Services | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									46	52	51
Adjustments									0	0
Total Revenue from Contracts with Customers									46	52
Operating Segments | IT and Managed Services | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									6	7	11
Adjustments									0	0
Total Revenue from Contracts with Customers									6	7
Operating Segments | IT and Managed Services | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Broadband
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									2,876	2,822	2,698
Operating Segments | Broadband | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Broadband | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Broadband | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Broadband | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Broadband | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									2,876	2,822	2,698
Adjustments									(215)	(213)
Total Revenue from Contracts with Customers									2,661	2,609
Operating Segments | Voice
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,881	2,173	2,531
Operating Segments | Voice | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Voice | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Voice | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Voice | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Voice | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									1,881	2,173	2,531
Adjustments									0	0
Total Revenue from Contracts with Customers									1,881	2,173
Operating Segments | Regulatory | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									634	729
Adjustments									(634)	(729)
Total Revenue from Contracts with Customers									0	0
Operating Segments | Other
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									251	392	491
Operating Segments | Other | International and Global Accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Other | Enterprise
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Other | Small and Medium Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Other | Wholesale
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									0	0	0
Operating Segments | Other | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue									251	392	$ 491
Adjustments									(24)	(33)
Total Revenue from Contracts with Customers									$ 227	$ 359