Pension and Postretirement Plans (Summary of Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Benefits
Components of Net Periodic Benefit Cost
Service cost	$ 1	$ 1
Interest cost	2	2
Expected return on plan assets	0	0
Amortization of prior service credit	(1)	0
Recognized net actuarial loss	0	0
Settlements	0	0
Net periodic benefit cost	2	3
U.S. | Pension Benefits
Components of Net Periodic Benefit Cost
Service cost	33	32
Interest cost	25	27
Expected return on plan assets	(41)	(36)
Amortization of prior service credit	0	0
Recognized net actuarial loss	14	13
Settlements	0	4
Net periodic benefit cost	31	40
Int’l. | Pension Benefits
Components of Net Periodic Benefit Cost
Service cost	7	6
Interest cost	6	6
Expected return on plan assets	(13)	(11)
Amortization of prior service credit	0	0
Recognized net actuarial loss	4	2
Settlements	0	0
Net periodic benefit cost	$ 4	$ 3