Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Decrease (increase) in current assets:
Receivables, net	$ 145	$ 817
Inventories	(126)	(291)
Prepaid expenses and other	(79)	53
Increase (decrease) in current liabilities:
Accounts payable	(322)	(306)
Accrued expenses	(131)	20
Taxes other than income taxes payable	(111)	(123)
Income taxes payable	(402)	(19)
Changes in current assets and current liabilities	(1,026)	151
Cash Flows Related to Interest and Income Taxes
Interest paid in excess of amount capitalized	127	128
Income taxes paid, net	$ 552	96
Capital Lease Obligations [Member]
Supplemental Cash Flow Elements (Textual)
Capital lease obligations incurred		490
Assets Held under Capital Leases [Member]
Supplemental Cash Flow Elements (Textual)
Capital lease assets recognized		$ 490