Segment Information - Reconciliation of Segments Operating Income to Consolidated Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Operating income	$ 7,675	$ 6,988	$ 21,641	$ 21,964
Severance charges (Note 8)	0	0	(339)	(195)
Other components of net periodic benefit credit (Note 8)	(688)	(218)	(1,197)	(655)
Gain on spectrum license transaction (Note 3)	0	0	0	126
Acquisition and integration related charges (Note 3)	(137)	(166)	(364)	(730)
Product realignment charges	0	0	(451)	0
Net gain on sale of divested business	0	0	0	1,774
Operating results from divested businesses	0	17	0	149
Equity in losses of unconsolidated businesses	(3)	(22)	(250)	(71)
Other income (expense), net	214	(291)	499	(719)
Interest expense	(1,211)	(1,164)	(3,634)	(3,514)
Income Before Provision For Income Taxes	6,675	5,511	18,256	17,660
Operating Segments
Segment Reporting Information [Line Items]
Operating income	8,461	7,668	24,834	22,407
Corporate and other
Segment Reporting Information [Line Items]
Operating income	$ 39	$ (313)	$ (842)	$ (912)