Post-Employment Benefits - General (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plans
Defined benefit plan net periodic benefit cost
Service cost - benefits earned during the period	$ 63	$ 76	$ 188	$ 221
Interest cost on projected benefit obligations	84	77	253	232
Expected return on plans assets	(177)	(169)	(533)	(511)
Net amortization of:
Actuarial loss, net	33	51	99	154
Prior service cost (credit)			1	1
Net cost - continuing operations	3	35	8	97
Post-employment Obligations and Other Long-term Liabilities:
Company contributions			337	71
Medical and Dental Plans
Defined benefit plan net periodic benefit cost
Service cost - benefits earned during the period	5	7	17	20
Interest cost on projected benefit obligations	13	12	39	36
Expected return on plans assets	(6)	(9)	(20)	(25)
Net amortization of:
Actuarial loss, net	6	8	17	25
Prior service cost (credit)	(8)	(11)	(24)	(34)
Net cost - continuing operations	$ 10	$ 7	29	22
Post-employment Obligations and Other Long-term Liabilities:
Company contributions			$ 11	$ 11