Pension and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended			93 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 7	$ 7
Interest cost	15	16	18
Expected return on plan assets	0	0	0
Amortization:
Actuarial loss	0	0	0
Prior service cost (credit)	0	(4)	(15)
Special termination benefit	0	4	0
Curtailment gain	0	0	0
Settlement loss	0	0	0
Net periodic benefit cost	22	23	10	$ (83)
United States Pension Benefits | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	3
Interest cost	118	134	147
Expected return on plan assets	(170)	(175)	(186)
Amortization:
Actuarial loss	53	50	46
Prior service cost (credit)	(3)	(3)	(3)
Special termination benefit	0	0	0
Curtailment gain	0	0	4
Settlement loss	0	0	0
Net periodic benefit cost	0	8	11
Foreign Pension Benefits | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	5	5
Interest cost	23	23	27
Expected return on plan assets	(32)	(30)	(30)
Amortization:
Actuarial loss	9	6	4
Prior service cost (credit)	0	0	0
Special termination benefit	0	0	0
Curtailment gain	(4)	0	(1)
Settlement loss	3	2	3
Net periodic benefit cost	4	6	8
Operating Income (Loss) | Other Postretirement Benefits
Amortization:
Net periodic benefit cost	7	7	7
Operating Income (Loss) | United States Pension Benefits | Pension Benefits
Amortization:
Net periodic benefit cost	2	2	3
Operating Income (Loss) | Foreign Pension Benefits | Pension Benefits
Amortization:
Net periodic benefit cost	5	5	5
Nonoperating Income (Expense) | Other Postretirement Benefits
Amortization:
Net periodic benefit cost	15	16	3
Nonoperating Income (Expense) | United States Pension Benefits | Pension Benefits
Amortization:
Net periodic benefit cost	(2)	6	8
Nonoperating Income (Expense) | Foreign Pension Benefits | Pension Benefits
Amortization:
Net periodic benefit cost	$ (1)	$ 1	$ 3