Pension and Postretirement Plans (Summary of Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits | United States
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 127	$ 136	$ 132
Interest cost	109	104	108
Expected return on plan assets	(143)	(169)	(146)
Amortization of prior service cost (credit)	0	0	3
Amortization of net actuarial loss (gain)	53	59	70
Settlements	8	72	83
Total net periodic benefit cost	154	202	250
Pension Benefits | Int’l.
Defined Benefit Plan Disclosure [Line Items]
Service cost	23	29	32
Interest cost	26	28	27
Expected return on plan assets	(44)	(46)	(40)
Amortization of prior service cost (credit)	(1)	(1)	(1)
Amortization of net actuarial loss (gain)	6	19	23
Settlements	0	0	0
Total net periodic benefit cost	10	29	41
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	6	6
Interest cost	9	7	8
Expected return on plan assets	0	0	0
Amortization of prior service cost (credit)	(2)	(1)	(2)
Amortization of net actuarial loss (gain)	(1)	0	0
Settlements	0	0	0
Total net periodic benefit cost	$ 11	$ 12	$ 12