Segment Information - Reconciliation of Segments Operating Income to Consolidated Income (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 income	$ 8,905	$ 7,678	$ 24,840	$ 21,618
Other components of net periodic benefit charges	(192)	(203)	(576)	(610)
Loss on spectrum license transaction	0	0	(223)	(1,195)
Equity in earnings (losses) of unconsolidated businesses	1	(9)	10	(34)
Other income (expense), net	269	(774)	1,172	(703)
Interest expense	(801)	(1,044)	(2,746)	(3,167)
Income Before Provision For Income Taxes	8,374	5,851	23,276	17,714
Operating Segments
Segment Reporting Information [Line Items]
Operating income	8,476	8,360	25,247	24,606
Corporate and other
Segment Reporting Information [Line Items]
Operating income	$ 621	$ (479)	$ 392	$ (1,183)