Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Net cash provided by (used in) operating activities included:
Interest paid (net of amounts capitalized)	$ (134)	$ (193)
Income taxes paid to taxing authorities	(282)	(43)
Noncash investing activities:
Receivable Related To Disposal Of Assets	0	742
Capital Expenditures Incurred but Not yet Paid	$ 303	$ 338