Pensions Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Cash contributions to retirement plans	$ 200	$ 43	$ 38
Fair value of investments contributed to defined benefit plans		16
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated Employer Contributions in Next Fiscal Year	35
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated Employer Contributions in Next Fiscal Year	65
Pension Plans, Defined Benefit [Member] | United States
Change in Projected Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	1,249	1,213
Business combinations		33
Interest costs	43	51	50
Actuarial (gains) losses	92	30
Benefits paid	(84)	(78)
Benefit Obligation at End of Year	1,300	1,249	1,213
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	944	945
Actual return on plan assets	161	71
Employer contribution	160	6
Benefits paid	(84)	(78)
Fair Value of Plan Assets at End of Year	1,181	944	945
Funded Status	(119)	(305)
Accumulated Benefit Obligation	1,300	1,249
Amounts Recognized in Balance Sheet [Abstract]
Current liability	(7)	(10)
Non-current liability	(112)	(295)
Net amount recognized	(119)	(305)
Amounts Recognized in Accumulated Other Comprehensive Loss [Abstract]
Net actuarial loss	156	171
Net amount recognized	$ 156	$ 171
Weighted Average Assumptions Used to Determine Benefit Obligation [Abstract]
Discount rate	3.55%	4.07%
Average rate of increase in employee compensation	4.00%	4.00%
Pension Plans, Defined Benefit [Member] | Foreign Plan [Member]
Change in Projected Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	$ 1,116	$ 1,036
Business combinations	185	1
Service costs	26	24	25
Interest costs	21	27	28
Settlements	(60)	(8)
Plan participants' contributions	5	4
Actuarial (gains) losses	(34)	150
Benefits paid	(37)	(30)
Currency translation and other	102	(88)
Benefit Obligation at End of Year	1,324	1,116	1,036
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	853	817
Business combinations	101
Actual return on plan assets	32	125
Employer contribution	37	50
Settlements	(60)	(8)
Plan participants' contributions	5	4
Benefits paid	(37)	(30)
Currency translation and other	80	(105)
Fair Value of Plan Assets at End of Year	1,011	853	817
Funded Status	(313)	(263)
Accumulated Benefit Obligation	1,256	1,048
Amounts Recognized in Balance Sheet [Abstract]
Non-current asset	100	63
Current liability	(10)	(6)
Non-current liability	(403)	(320)
Net amount recognized	(313)	(263)
Amounts Recognized in Accumulated Other Comprehensive Loss [Abstract]
Net actuarial loss	126	170
Prior service credits	10	8
Net amount recognized	$ 136	$ 178
Weighted Average Assumptions Used to Determine Benefit Obligation [Abstract]
Discount rate	2.10%	1.95%
Average rate of increase in employee compensation	2.59%	3.09%
Postretirement Benefits [Member]
Change in Projected Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	$ 50	$ 49
Business combinations	6
Service costs	1	1
Interest costs	2	2
Plan participants' contributions	1	1
Actuarial (gains) losses	6	1
Benefits paid	(4)	(4)
Currency translation and other	1
Benefit Obligation at End of Year	63	50	49
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	8	7
Actual return on plan assets	1	1
Employer contribution	3	3
Plan participants' contributions	1	1
Benefits paid	(4)	(4)
Fair Value of Plan Assets at End of Year	9	8	$ 7
Funded Status	(54)	(42)
Amounts Recognized in Balance Sheet [Abstract]
Non-current asset	6	4
Current liability	(3)	(3)
Non-current liability	(57)	(43)
Net amount recognized	(54)	(42)
Amounts Recognized in Accumulated Other Comprehensive Loss [Abstract]
Net actuarial loss	11	6
Net amount recognized	$ 11	$ 6
Weighted Average Assumptions Used to Determine Benefit Obligation [Abstract]
Discount rate	3.43%	3.77%
Initial healthcare cost trend rate	6.73%	6.70%
Ultimate healthcare cost trend rate	5.04%	5.08%
Postretirement Benefits [Member] | Minimum [Member]
Weighted Average Assumptions Used to Determine Benefit Obligation [Abstract]
Year that Healthcare Cost Rate Reaches Ultimate Trend Rate	2018
Postretirement Benefits [Member] | Maximum [Member]
Weighted Average Assumptions Used to Determine Benefit Obligation [Abstract]
Year that Healthcare Cost Rate Reaches Ultimate Trend Rate	2033