Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Changes in accumulated other comprehensive income (loss), net of income taxes
Beginning of the period			$ 32,784
Net current period comprehensive income (loss)	$ (174)	$ 36	(294)	$ (579)
End of the period	34,422		34,422
Cumulative Foreign Currency Translation Adjustments
Changes in accumulated other comprehensive income (loss), net of income taxes
Beginning of the period	(5,230)	(5,713)	(4,859)	(4,924)
Other comprehensive income (loss) before reclassifications	(391)	112	(762)	(677)
Amounts reclassified from accumulated other comprehensive income	0	0
Net current period comprehensive income (loss)	(391)	112	(762)	(677)
End of the period	(5,621)	(5,601)	(5,621)	(5,601)
Net Actuarial (Losses) and Prior Service (Costs) and Credits
Changes in accumulated other comprehensive income (loss), net of income taxes
Beginning of the period	(3,738)	(3,446)	(3,871)	(3,540)
Other comprehensive income (loss) before reclassifications	16	(21)	26	(23)
Amounts reclassified from accumulated other comprehensive income	62	49	185	145
Net current period comprehensive income (loss)	78	28	211	122
End of the period	(3,660)	(3,418)	(3,660)	(3,418)
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	(98)	79	(216)	(1)
Other comprehensive income (loss) before reclassifications	70	(74)	138	35
Amounts reclassified from accumulated other comprehensive income	69	(30)	119	(59)
Net current period comprehensive income (loss)	139	(104)	257	(24)
End of the period	$ 41	$ (25)	$ 41	$ (25)