Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Other comprehensive income (loss)	$ (536)	$ 60
Net Effect of Exchange Rate Fluctuations
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(813)	(889)
Change before reclassifications	(564)	46
Other comprehensive income (loss)	(564)	46
Balance at end of the period	(1,377)	(843)
Change in Certain Derivative Instruments
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(14)	(18)
Change before reclassifications	(2)	(2)
Amounts reclassified from accumulated other comprehensive income	11	3
Translation effect	(1)	2
Tax effect	(2)	2
Other comprehensive income (loss)	6	5
Balance at end of the period	(8)	(13)
Employee Benefit Plans
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(1,016)	(1,061)
Change before reclassifications	(2)	(2)
Amounts reclassified from accumulated other comprehensive income	17	13
Translation effect	16	(5)
Other comprehensive income (loss)	31	6
Balance at end of the period	(985)	(1,055)
Accumulated Other Comprehensive Loss.
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(1,843)	(1,968)
Change before reclassifications	(568)	42
Amounts reclassified from accumulated other comprehensive income	28	16
Translation effect	15	(3)
Tax effect	(2)	2
Other comprehensive income (loss)	(527)	57
Balance at end of the period	$ (2,370)	$ (1,911)