Operating Financial Information for Reportable Segments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Operating Revenues	$ 30,937	$ 33,158	$ 93,640	$ 97,366
Operating income (Loss)	6,540	7,535	19,036	23,316
Wireless
Segment Reporting Information [Line Items]
Operating Revenues	22,101	23,005	65,809	67,946
Operating income (Loss)	7,647	7,668	23,544	23,174
Wireline
Segment Reporting Information [Line Items]
Operating Revenues	7,787	7,967	23,533	24,030
Operating income (Loss)	156	(109)	(374)	(528)
Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	29,888	30,972	89,342	91,976
Operating income (Loss)	7,803	7,559	23,170	22,646
Operating Segments | Wireless
Segment Reporting Information [Line Items]
Operating Revenues	22,020	22,980	65,551	67,868
Operating Segments | Wireless | Service Revenue
Segment Reporting Information [Line Items]
Operating Revenues	16,647	17,580	50,108	53,146
Operating Segments | Wireless | Equipment Revenue
Segment Reporting Information [Line Items]
Operating Revenues	4,124	4,292	11,782	11,526
Operating Segments | Wireless | Other External Operating Non-Service Revenues
Segment Reporting Information [Line Items]
Operating Revenues	1,249	1,108	3,661	3,196
Operating Segments | Wireline
Segment Reporting Information [Line Items]
Operating Revenues	7,558	7,722	22,827	23,295
Operating Segments | Wireline | Mass Markets Consumer Retail
Segment Reporting Information [Line Items]
Operating Revenues	3,174	3,168	9,519	9,470
Operating Segments | Wireline | Mass Markets Small Business
Segment Reporting Information [Line Items]
Operating Revenues	411	434	1,241	1,320
Operating Segments | Wireline | Mass Markets
Segment Reporting Information [Line Items]
Operating Revenues	3,585	3,602	10,760	10,790
Operating Segments | Wireline | Global Enterprise
Segment Reporting Information [Line Items]
Operating Revenues	2,886	2,987	8,748	9,040
Operating Segments | Wireline | Global Wholesale
Segment Reporting Information [Line Items]
Operating Revenues	1,009	1,046	3,071	3,209
Operating Segments | Wireline | Other
Segment Reporting Information [Line Items]
Operating Revenues	78	87	248	256
Operating Segments | Reportable Segment
Segment Reporting Information [Line Items]
Operating Revenues	29,578	30,702	88,378	91,163
Intersegment Revenues | Wireless
Segment Reporting Information [Line Items]
Operating Revenues	81	25	258	78
Intersegment Revenues | Wireline
Segment Reporting Information [Line Items]
Operating Revenues	229	245	706	735
Intersegment Revenues | Reportable Segment
Segment Reporting Information [Line Items]
Operating Revenues	$ 310	$ 270	$ 964	$ 813