Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Decrease (increase) in current assets:
Receivables, net	$ (595)	$ 1,396
Inventories	(46)	123
Prepaid expenses and other	(35)	86
Increase (decrease) in current liabilities:
Accounts payable	661	(942)
Accrued expenses	(83)	262
Taxes other than income taxes payable	28	(41)
Income taxes payable	(375)	(25)
Changes in current assets and current liabilities	(445)	859
Cash Flows Related to Interest and Income Taxes
Interest paid in excess of amount capitalized	248	235
Income taxes paid, net	$ 817	263
Capital Lease Obligations [Member]
Supplemental Cash Flow Information (Textual)
Capital lease obligations incurred		490
Assets Held under Capital Leases [Member]
Supplemental Cash Flow Information (Textual)
Capital lease assets recognized		$ 490