Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 5,902	$ 4,090	$ 11,847	$ 8,299
Adjustments	(325)		(636)
Total Revenue from Contracts with Customers	5,577		11,211
Transferred at Point in Time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue from Contracts with Customers	42		81
Transferred over Time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenue from Contracts with Customers	5,535		11,130
Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	4,365	2,470	8,748	5,060
Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	1,352	1,437	2,731	2,884
Operating segments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	5,717	3,907	11,479	7,944
Operating segments | Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	4,365	2,470	8,748	5,060
Adjustments	(80)		(147)
Total Revenue from Contracts with Customers	4,285		8,601
Operating segments | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	1,352	1,437	2,731	2,884
Adjustments	(60)		(121)
Total Revenue from Contracts with Customers	1,292		2,610
Operating segments | IP & Data Services | Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	1,748	744	3,485	1,501
Adjustments	0		0
Total Revenue from Contracts with Customers	1,748		3,485
Operating segments | IP & Data Services | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	85	107	179	210
Adjustments	(7)		(16)
Total Revenue from Contracts with Customers	78		163
Operating segments | Transport & Infrastructure | Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	1,342	797	2,691	1,691
Adjustments	(80)		(147)
Total Revenue from Contracts with Customers	1,262		2,544
Operating segments | Transport & Infrastructure | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	722	683	1,451	1,366
Adjustments	(53)		(105)
Total Revenue from Contracts with Customers	669		1,346
Operating segments | Voice & Collaboration | Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	1,111	767	2,247	1,554
Adjustments	0		0
Total Revenue from Contracts with Customers	1,111		2,247
Operating segments | Voice & Collaboration | Consumer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	545	647	1,101	1,308
Adjustments	0		0
Total Revenue from Contracts with Customers	545		1,101
Operating segments | IT & Managed Services | Business
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	164	162	325	314
Adjustments	0		0
Total Revenue from Contracts with Customers	164		325
Corporate, Non-Segment
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	185	183	368	355
Adjustments	(185)		(368)
Total Revenue from Contracts with Customers	0		0
Corporate, Non-Segment | Regulatory Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	185	$ 183	368	$ 355
Adjustments	(185)		(368)
Total Revenue from Contracts with Customers	$ 0		$ 0