Equity and Accumulated Other Comprehensive Income - Changes in AOCI (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			$ 62,835
Other comprehensive income (loss)			(744)
Amounts reclassified to net income			(1,066)
Net other comprehensive income (loss)			(1,810)
Ending Balance	$ 66,530	$ 60,312	66,530	$ 60,312
Foreign  currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			(584)
Other comprehensive income (loss)			81
Amounts reclassified to net income			0
Net other comprehensive income (loss)			81
Ending Balance	(503)		(503)
Unrealized loss on cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			(816)
Other comprehensive income (loss)			(832)
Amounts reclassified to net income			(559)
Net other comprehensive income (loss)			(1,391)
Ending Balance	(2,207)		(2,207)
Unrealized gain on marketable securities
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			27
Other comprehensive income (loss)			7
Amounts reclassified to net income			0
Net other comprehensive income (loss)			7
Ending Balance	34		34
Defined benefit pension and postretirement plans
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			2,371
Other comprehensive income (loss)			0
Amounts reclassified to net income			(507)
Net other comprehensive income (loss)			(507)
Ending Balance	1,864		1,864
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance	(1,274)	1,447	998	2,370
Net other comprehensive income (loss)	462	(343)	(1,810)	(1,266)
Ending Balance	$ (812)	$ 1,104	$ (812)	$ 1,104