Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Other comprehensive income (loss)	$ 60	$ 8	$ (476)	$ 68
Net Effect of Exchange Rate Fluctuations
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(1,377)	(843)	(813)	(889)
Change before reclassifications	56	13	(508)	59
Other comprehensive income (loss)	56	13	(508)	59
Balance at end of the period	(1,321)	(830)	(1,321)	(830)
Change in Certain Derivative Instruments
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(8)	(13)	(14)	(18)
Change before reclassifications	35	(14)	(17)	(24)
Amounts reclassified from accumulated other comprehensive income (loss)	(50)	4	11	14
Translation effect	1	1		3
Tax effect	1		(1)	3
Other comprehensive income (loss)	(13)	(9)	(7)	(4)
Balance at end of the period	(21)	(22)	(21)	(22)
Employee Benefit Plans
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(985)	(1,055)	(1,016)	(1,061)
Change before reclassifications	7		5	(2)
Amounts reclassified from accumulated other comprehensive income (loss)	17	12	34	25
Translation effect	(3)	4	13	(1)
Tax effect	(2)		(2)
Other comprehensive income (loss)	19	16	50	22
Balance at end of the period	(966)	(1,039)	(966)	(1,039)
Accumulated Other Comprehensive Loss.
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(2,370)	(1,911)	(1,843)	(1,968)
Change before reclassifications	98	(1)	(520)	33
Amounts reclassified from accumulated other comprehensive income (loss)	(33)	16	45	39
Translation effect	(2)	5	13	2
Tax effect	(1)		(3)	3
Other comprehensive income (loss)	62	20	(465)	77
Balance at end of the period	$ (2,308)	$ (1,891)	$ (2,308)	$ (1,891)