Segment Information - Operating Financial Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 31,543	$ 32,894	$ 93,600	$ 97,093
Operating Income	7,678	8,180	21,618	23,739
Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	4,112	5,141	11,996	14,792
Service and Other
Segment Reporting Information [Line Items]
Operating revenues	27,431	27,753	81,604	82,301
Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	3,036	3,054	9,111	9,072
Wireless service
Segment Reporting Information [Line Items]
Operating revenues	16,432	16,383	48,737	48,665
Consumer
Segment Reporting Information [Line Items]
Operating revenues	21,672	22,641	64,431	66,672
Consumer | Service
Segment Reporting Information [Line Items]
Operating revenues	16,255	16,432	48,496	49,043
Consumer | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	3,403	4,256	9,989	12,326
Consumer | Other
Segment Reporting Information [Line Items]
Operating revenues	2,014	1,953	5,946	5,303
Consumer | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	2,773	2,811	8,326	8,347
Consumer | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	13,442	13,533	40,005	40,346
Business
Segment Reporting Information [Line Items]
Operating revenues	7,733	7,870	22,858	23,331
Business | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	709	880	2,000	2,500
Business | Small and Medium Business
Segment Reporting Information [Line Items]
Operating revenues	2,737	2,894	8,132	8,379
Business | Global Enterprise
Segment Reporting Information [Line Items]
Operating revenues	2,594	2,714	7,811	8,077
Business | Public Sector and Other
Segment Reporting Information [Line Items]
Operating revenues	1,639	1,472	4,636	4,435
Business | Wholesale
Segment Reporting Information [Line Items]
Operating revenues	763	790	2,279	2,440
Business | Service and Other
Segment Reporting Information [Line Items]
Operating revenues	7,000	7,000	20,900	20,900
Business | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	263	243	785	725
Business | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	2,990	2,850	8,732	8,319
Total reportable segments
Segment Reporting Information [Line Items]
Operating revenues	29,405	30,511	87,289	90,003
Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	80	80	237	218
Intersegment Eliminations | Consumer
Segment Reporting Information [Line Items]
Operating revenues	64	65	183	177
Intersegment Eliminations | Business
Segment Reporting Information [Line Items]
Operating revenues	16	15	54	41
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	29,485	30,591	87,526	90,221
Operating Income	8,360	8,466	24,606	25,171
Operating Segments | Consumer
Segment Reporting Information [Line Items]
Operating revenues	21,736	22,706	64,614	66,849
Operating Income	7,437	7,489	21,783	22,075
Operating Segments | Business
Segment Reporting Information [Line Items]
Operating revenues	7,749	7,885	22,912	23,372
Operating Income	$ 923	$ 977	$ 2,823	$ 3,096