Accounting For Certain Long-Lived Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Proved oil and gas properties, other property, plant and equipment and other assets carrying amount	$ 667	$ 9,154
Amortization and impairments of unproved oil and gas property costs including amortization of capitalized interest	291	288	$ 168
Proved oil and gas properties, other property, plant and equipment, and other assets written down to fair value	537	2,828
Pretax impairment charges for proved oil and gas properties, other property, plant and equipment and other assets	$ 130	6,326
Net of tax impairment charges for proved oil and gas properties, other property, plant and equipment and other assets		$ 4,141