Segment Information - Operating Financial Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 31,610	$ 32,128
Operating Income	6,579	7,709
Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	4,129	4,931
Service and Other
Segment Reporting Information [Line Items]
Operating revenues	27,481	27,197
Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	3,061	3,007
Wireless service
Segment Reporting Information [Line Items]
Operating revenues	16,357	16,051
Consumer
Segment Reporting Information [Line Items]
Operating revenues	21,706	22,098
Consumer | Service
Segment Reporting Information [Line Items]
Operating revenues	16,343	16,261
Consumer | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	3,377	4,166
Consumer | Other
Segment Reporting Information [Line Items]
Operating revenues	1,986	1,671
Consumer | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	2,799	2,764
Consumer | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	13,476	13,357
Business
Segment Reporting Information [Line Items]
Operating revenues	7,662	7,706
Business | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	752	765
Business | Global Enterprise
Segment Reporting Information [Line Items]
Operating revenues	2,630	2,690
Business | Small and Medium Business
Segment Reporting Information [Line Items]
Operating revenues	2,798	2,704
Business | Public Sector and Other
Segment Reporting Information [Line Items]
Operating revenues	1,474	1,471
Business | Wholesale
Segment Reporting Information [Line Items]
Operating revenues	760	841
Business | Service and Other
Segment Reporting Information [Line Items]
Operating revenues	6,900	6,900
Business | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	262	243
Business | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	2,881	2,694
Total reportable segments
Segment Reporting Information [Line Items]
Operating revenues	29,368	29,804
Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	78	63
Intersegment Eliminations | Consumer
Segment Reporting Information [Line Items]
Operating revenues	59	50
Intersegment Eliminations | Business
Segment Reporting Information [Line Items]
Operating revenues	19	13
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	29,446	29,867
Operating Income	8,236	8,298
Operating Segments | Consumer
Segment Reporting Information [Line Items]
Operating revenues	21,765	22,148
Operating Income	7,282	7,250
Operating Segments | Business
Segment Reporting Information [Line Items]
Operating revenues	7,681	7,719
Operating Income	$ 954	$ 1,048