Accounting For Certain Long-Lived Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Proved oil and gas properties carrying amount	$ 408	$ 139
Proved oil and gas properties, other property, plant and equipment, and other assets written down to fair value	201	18
Pretax impairment chages for proved oil and gas properties, other property, plant and equipment and other assets	207	121
Amortization and Impairments of Unproved Oil and Gas Property Including Amortization of Capitalized Interest	$ 220	$ 173	$ 211