Pension and Other Postretirement Benefits, Changes in Benefit Obligations, Plan Assets and Funded Status and Aggregate Balance Sheet Impact (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets and (liabilities) recognized on the consolidated balance sheets consist of [Abstract]
Non-current liabilities	$ (1,211)	$ (1,313)
Pension Plans [Member]
Change in benefit obligation [Abstract]
Benefit obligation at the beginning of the year	4,228	3,758
Service cost	103	97	$ 94
Interest cost	143	142	135
Plan participants' contributions	2	2
Amendments	(13)	0
Actuarial loss (gain)	(340)	391
Foreign currency exchange rate changes	(27)	22
Curtailments and special termination benefits	0	2
Benefits paid	(159)	(186)
Benefit obligation at the end of the year	3,937	4,228	3,758
Change in plan assets [Abstract]
Fair value of plan assets at the beginning of the year	3,047	2,721
Actual return on plan assets	(119)	391
Employer contributions	96	97
Plan participants' contributions	2	2
Foreign currency exchange rate changes	(27)	22
Benefits paid	(159)	(186)
Fair value of plan assets at the end of the year	2,840	3,047	2,721
Unfunded status at the end of the year	(1,097)	(1,181)
Assets and (liabilities) recognized on the consolidated balance sheets consist of [Abstract]
Non-current assets	40	48
Current liabilities	(8)	(6)
Non-current liabilities	(1,129)	(1,223)
Total	(1,097)	(1,181)
Postretirement Benefit Plans [Member]
Change in benefit obligation [Abstract]
Benefit obligation at the beginning of the year	165	177
Service cost	2	2	2
Interest cost	5	5	6
Plan participants' contributions	5	5
Amendments	0	0
Actuarial loss (gain)	(11)	(13)
Foreign currency exchange rate changes	(2)	2
Curtailments and special termination benefits	0	0
Benefits paid	(14)	(13)
Benefit obligation at the end of the year	150	165	177
Change in plan assets [Abstract]
Fair value of plan assets at the beginning of the year	67	60
Actual return on plan assets	(3)	8
Employer contributions	6	7
Plan participants' contributions	5	5
Foreign currency exchange rate changes	0	0
Benefits paid	(14)	(13)
Fair value of plan assets at the end of the year	61	67	$ 60
Unfunded status at the end of the year	(89)	(98)
Assets and (liabilities) recognized on the consolidated balance sheets consist of [Abstract]
Non-current assets	0	0
Current liabilities	(7)	(8)
Non-current liabilities	(82)	(90)
Total	$ (89)	$ (98)