Financial Instruments and Risk Management (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of days from period end	2 days
Debt, Long-term and Short-term, Combined Amount	$ 10,457	$ 10,457
Foreign Currency Derivatives [Abstract]
Maximum term of currency derivative instruments (in years)		1 year
Long-term Debt, Percentage Bearing Fixed Interest, Amount	10,400	$ 10,400	$ 10,400
Estimate of Fair Value, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	10,876	10,876	12,457
Estimate of Fair Value, Fair Value Disclosure | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	0	0	0
Estimate of Fair Value, Fair Value Disclosure | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	6,726	6,726	3,285
Estimate of Fair Value, Fair Value Disclosure | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	4,150	4,150	9,172
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, Long-term and Short-term, Combined Amount			10,942
Foreign Exchange Contract [Member] | Other current assets | Level 2
Foreign Currency Derivatives [Abstract]
Derivative, Notional Amount	591	591	633
Foreign Exchange Contract [Member] | Other assets | Level 2
Foreign Currency Derivatives [Abstract]
Derivative, Notional Amount	$ 100	$ 100	$ 100