Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Decrease (increase) in current assets:
Receivables, net	$ (870)	$ (1,531)	$ 1,294
Inventories	(516)	771	(222)
Prepaid expenses and other	151	47	(149)
Increase (decrease) in current liabilities:
Accounts payable	1,842	1,556	(1,787)
Accrued expenses	21	117	(40)
Taxes other than income taxes payable	172	82	(74)
Income taxes payable	489	(66)	(328)
Changes in current assets and current liabilities	1,289	976	(1,306)
Cash Flows Related to Interest and Income Taxes
Interest paid in excess of amount capitalized	457	427	416
Income taxes paid, net	410	444	2,093
Supplemental Cash Flow Elements (Textual)
Payment of long-term liability to joint venture partner	$ 26	194	$ (25)
Owner-Method Joint Venture Investment [Member]
Supplemental Cash Flow Elements (Textual)
Payment of long-term liability to joint venture partner		$ 137