Segment Information - Operating Financial Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Operating revenues	$ 32,915	$ 31,543	$ 99,546	$ 93,600
Operating Income	8,905	7,678	24,840	21,618
Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	5,350	4,112	15,837	11,996
Service revenues and other
Segment Reporting Information [Line Items]
Operating revenues	27,565	27,431	83,709	81,604
Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	3,180	3,036	9,492	9,111
Wireless service
Segment Reporting Information [Line Items]
Operating revenues	17,079	16,432	50,707	48,737
Consumer
Segment Reporting Information [Line Items]
Operating revenues	23,271	21,672	69,427	64,431
Consumer | Service
Segment Reporting Information [Line Items]
Operating revenues	16,889	16,255	50,159	48,496
Consumer | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	4,530	3,403	13,461	9,989
Consumer | Other
Segment Reporting Information [Line Items]
Operating revenues	1,852	2,014	5,807	5,946
Consumer | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	2,893	2,773	8,648	8,326
Consumer | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	13,982	13,442	41,460	40,005
Business
Segment Reporting Information [Line Items]
Operating revenues	7,673	7,733	23,179	22,858
Business | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	820	709	2,400	2,000
Business | Small and Medium Business
Segment Reporting Information [Line Items]
Operating revenues	2,929	2,737	8,644	8,132
Business | Global Enterprise
Segment Reporting Information [Line Items]
Operating revenues	2,551	2,594	7,690	7,811
Business | Public Sector and Other
Segment Reporting Information [Line Items]
Operating revenues	1,548	1,639	4,807	4,636
Business | Wholesale
Segment Reporting Information [Line Items]
Operating revenues	645	763	2,038	2,279
Business | Service revenues and other
Segment Reporting Information [Line Items]
Operating revenues	6,900	7,000	20,900	20,900
Business | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	287	263	844	785
Business | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	3,097	2,990	9,247	8,732
Total reportable segments
Segment Reporting Information [Line Items]
Operating revenues	30,944	29,405	92,606	87,289
Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	73	80	229	237
Intersegment Eliminations | Consumer
Segment Reporting Information [Line Items]
Operating revenues	57	64	176	183
Intersegment Eliminations | Business
Segment Reporting Information [Line Items]
Operating revenues	16	16	53	54
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	31,017	29,485	92,835	87,526
Operating Income	8,476	8,360	25,247	24,606
Operating Segments | Consumer
Segment Reporting Information [Line Items]
Operating revenues	23,328	21,736	69,603	64,614
Operating Income	7,590	7,437	22,606	21,783
Operating Segments | Business
Segment Reporting Information [Line Items]
Operating revenues	7,689	7,749	23,232	22,912
Operating Income	$ 886	$ 923	$ 2,641	$ 2,823