Segment Information - Reconciliation of Segments Operating Income to Consolidated Income (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 income	$ 7,678	$ 8,180	$ 21,618	$ 23,739
Other components of net periodic benefit charges	(203)	(203)	(610)	(610)
Loss on spectrum license transaction	0	0	(1,195)	0
Net gain from dispositions of assets and businesses	0	261	0	261
Net gain from dispositions of assets and businesses			0	(94)
Equity in losses of unconsolidated businesses	(9)	(1)	(34)	(20)
Other expense, net	(774)	(110)	(703)	(1,127)
Interest expense	(1,044)	(1,146)	(3,167)	(3,571)
Income Before Provision For Income Taxes	5,851	6,923	17,714	19,021
Operating Segments
Segment Reporting Information [Line Items]
Operating income	8,360	8,466	24,606	25,171
Corporate and other
Segment Reporting Information [Line Items]
Operating income	$ (479)	$ (344)	$ (1,183)	$ (1,083)