Pension and Other Postretirement Benefits (Components of Net Periodic Pension and Other Postretirement Benefits Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 0	$ 0	$ 1
Interest cost	6	6	7
Amortization of actuarial loss	4	5	4
Amortization of prior service cost (credit)	(40)	(41)	(37)
Net periodic benefit cost (credit)	(30)	(30)	(25)
U.S. Plans | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	14	14	14
Interest cost	50	50	63
Expected return on plan assets	(83)	(91)	(100)
Amortization of actuarial loss	52	50	50
Amortization of prior service cost (credit)	1	1	0
Net periodic benefit cost (credit)	34	24	27
Non-U.S. Plans | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	22	21	24
Interest cost	75	101	127
Expected return on plan assets	(146)	(157)	(172)
Amortization of actuarial loss	42	50	55
Amortization of prior service cost (credit)	(11)	(12)	(13)
Net periodic benefit cost (credit)	$ (18)	$ 3	$ 21