Post-Employment Benefits - (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans
Defined benefit plan net periodic benefit cost
Service cost - benefits earned during the period	$ 85	$ 63	$ 251	$ 188
Interest cost on projected benefit obligations	75	84	224	253
Expected return on plans assets	(193)	(177)	(576)	(533)
Net amortization of:
Actuarial loss, net	64	33	191	99
Prior service cost (credit)			1	1
Net cost - continuing operations	31	3	91	8
Post-employment Obligations and Other Long-term Liabilities:
Company contributions			350	337
Medical and Dental Plans
Defined benefit plan net periodic benefit cost
Service cost - benefits earned during the period	12	5	35	17
Interest cost on projected benefit obligations	11	13	32	39
Expected return on plans assets	(7)	(6)	(21)	(20)
Net amortization of:
Actuarial loss, net	5	6	15	17
Prior service cost (credit)	(7)	(8)	(21)	(24)
Net cost - continuing operations	$ 14	$ 10	40	29
Post-employment Obligations and Other Long-term Liabilities:
Company contributions			$ 11	$ 11