Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Changes in accumulated other comprehensive income (loss), net of income taxes
Beginning of the period			$ 31,088
Net current period comprehensive income (loss)	$ 36	$ (398)	(579)	$ (177)
End of the period	31,386		31,386
Cumulative Foreign Currency Translation Adjustments
Changes in accumulated other comprehensive income (loss), net of income taxes
Beginning of the period	(5,713)	(4,699)	(4,924)	(4,912)
Other comprehensive income (loss) before reclassifications	112	(478)	(677)	(265)
Net current period comprehensive income (loss)	112	(478)	(677)	(265)
End of the period	(5,601)	(5,177)	(5,601)	(5,177)
Net Actuarial (Losses) and Prior Service (Costs) and Credits
Changes in accumulated other comprehensive income (loss), net of income taxes
Beginning of the period	(3,446)	(2,677)	(3,540)	(2,726)
Other comprehensive income (loss) before reclassifications	(21)	7	(23)	9
Amounts reclassified from accumulated other comprehensive income	49	24	145	71
Net current period comprehensive income (loss)	28	31	122	80
End of the period	(3,418)	(2,646)	(3,418)	(2,646)
Cumulative Gains (Losses) on Derivative Instruments Designated as Cash Flow Hedges
Changes in accumulated other comprehensive income (loss), net of income taxes
Beginning of the period	79	11	(1)	52
Other comprehensive income (loss) before reclassifications	(74)	67	35	48
Amounts reclassified from accumulated other comprehensive income	(30)	(18)	(59)	(40)
Net current period comprehensive income (loss)	(104)	49	(24)	8
End of the period	$ (25)	$ 60	$ (25)	$ 60