Income Taxes (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($)
Domestic Tax Authority [Member]
Income Tax [Line Items]
Operating Loss Carryforwards	$ 1,800
WPX Merger [Member]
Income Tax [Line Items]
Deferred income taxes	250
Merger [Member]
Income Tax [Line Items]
Other income tax expense benefit	$ 18