Pension and Postretirement Plans (Summary of Amounts Recognized in Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss) arising during the period	$ (156)	$ (16)	$ (1)
Prior service credit arising during the period	2	0	$ 0
Pension Benefits | United States
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial loss (gain)	523	539
Unrecognized prior service credit	0	0
Net actuarial gain (loss) arising during the period	(45)	(125)
Curtailment gain	0	0
Amortization of net actuarial loss (gain) and settlements	61	131
Prior service credit arising during the period	0	0
Amortization of prior service credit	0	0
Total recognized in other comprehensive income (loss)	16	6
Pension Benefits | Int’l.
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial loss (gain)	164	64
Unrecognized prior service credit	(2)	(3)
Net actuarial gain (loss) arising during the period	(106)	102
Curtailment gain	0	5
Amortization of net actuarial loss (gain) and settlements	6	19
Prior service credit arising during the period	0	0
Amortization of prior service credit	(1)	(1)
Total recognized in other comprehensive income (loss)	(101)	125
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial loss (gain)	0	(8)
Unrecognized prior service credit	(6)	(6)
Net actuarial gain (loss) arising during the period	(7)	9
Curtailment gain	0	0
Amortization of net actuarial loss (gain) and settlements	(1)	0
Prior service credit arising during the period	2	0
Amortization of prior service credit	(2)	(1)
Total recognized in other comprehensive income (loss)	$ (8)	$ 8