Accounting For Suspended Exploratory Well Costs (Narrative) (Details) $ in Millions	Dec. 31, 2019 USD ($) Projects	Dec. 31, 2018 USD ($) Projects	Dec. 31, 2017 USD ($) Projects	Dec. 31, 2016 USD ($)
Exploratory Wells Drilled [Line Items]
Number of projects that have exploratory well costs capitalized for a period of greater than one year	46	52	46
Number of projects that have drilling in the preceding twelve months or exploratory activity planned in the next two years as of December 31, 2019	14
Number of projects with completed exploratory activity progressing toward development as of December 31, 2019	32
Capitalized exploratory well costs | $	$ 4,613	$ 4,160	$ 3,700	$ 4,477
32 Projects [Member]
Exploratory Wells Drilled [Line Items]
Capitalized exploratory well costs | $	$ 3,176