Equity and Accumulated Other Comprehensive Income - Changes in AOCI (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			$ 62,835
Other comprehensive income (loss)			(2,103)
Amounts reclassified to net income			(169)
Net other comprehensive income (loss)			(2,272)
Ending Balance	$ 64,113	$ 57,947	64,113	$ 57,947
Foreign  currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			(584)
Other comprehensive income (loss)			(43)
Amounts reclassified to net income			0
Net other comprehensive income (loss)			(43)
Ending Balance	(627)		(627)
Unrealized loss on cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			(816)
Other comprehensive income (loss)			(2,065)
Amounts reclassified to net income			169
Net other comprehensive income (loss)			(1,896)
Ending Balance	(2,712)		(2,712)
Unrealized gain on marketable securities
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance			27
Other comprehensive income (loss)			5
Amounts reclassified to net income			0
Net other comprehensive income (loss)			5
Ending Balance	32		32
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			(338)
Net other comprehensive income (loss)			(338)
Ending Balance	2,033		2,033
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance	(1,502)	2,216	998	2,370
Net other comprehensive income (loss)	228	(769)	(2,272)	(923)
Ending Balance	$ (1,274)	$ 1,447	$ (1,274)	$ 1,447