Segment Information - Operating Financial Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 30,447	$ 32,071	$ 62,057	$ 64,199
Operating Income	7,361	7,850	13,940	15,559
Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	3,755	4,720	7,884	9,651
Service and Other
Segment Reporting Information [Line Items]
Operating revenues	26,692	27,351	54,173	54,548
Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	3,014	3,011	6,075	6,018
Wireless service
Segment Reporting Information [Line Items]
Operating revenues	15,948	16,231	32,305	32,282
Consumer
Segment Reporting Information [Line Items]
Operating revenues	21,053	21,934	42,759	44,031
Consumer | Service
Segment Reporting Information [Line Items]
Operating revenues	15,898	16,350	32,241	32,611
Consumer | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	3,209	3,904	6,586	8,070
Consumer | Other
Segment Reporting Information [Line Items]
Operating revenues	1,946	1,680	3,932	3,350
Consumer | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	2,754	2,772	5,553	5,536
Consumer | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	13,087	13,456	26,563	26,813
Business
Segment Reporting Information [Line Items]
Operating revenues	7,463	7,756	15,125	15,461
Business | Wireless equipment
Segment Reporting Information [Line Items]
Operating revenues	546	814	1,300	1,600
Business | Small and Medium Business
Segment Reporting Information [Line Items]
Operating revenues	2,597	2,781	5,395	5,485
Business | Global Enterprise
Segment Reporting Information [Line Items]
Operating revenues	2,587	2,673	5,217	5,363
Business | Public Sector and Other
Segment Reporting Information [Line Items]
Operating revenues	1,523	1,492	2,997	2,963
Business | Wholesale
Segment Reporting Information [Line Items]
Operating revenues	756	810	1,516	1,650
Business | Service and Other
Segment Reporting Information [Line Items]
Operating revenues	7,000	7,000	13,900	13,900
Business | Fios revenues
Segment Reporting Information [Line Items]
Operating revenues	260	239	522	482
Business | Wireless service
Segment Reporting Information [Line Items]
Operating revenues	2,861	2,775	5,742	5,469
Total reportable segments
Segment Reporting Information [Line Items]
Operating revenues	28,516	29,690	57,884	59,492
Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	79	73	157	138
Intersegment Eliminations | Consumer
Segment Reporting Information [Line Items]
Operating revenues	60	61	119	112
Intersegment Eliminations | Business
Segment Reporting Information [Line Items]
Operating revenues	19	12	38	26
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	28,595	29,763	58,041	59,630
Operating Income	8,010	8,407	16,246	16,705
Operating Segments | Consumer
Segment Reporting Information [Line Items]
Operating revenues	21,113	21,995	42,878	44,143
Operating Income	7,064	7,336	14,346	14,586
Operating Segments | Business
Segment Reporting Information [Line Items]
Operating revenues	7,482	7,768	15,163	15,487
Operating Income	$ 946	$ 1,071	$ 1,900	$ 2,119