Acquisition and Divestitures (Schedule of Pro Forma Adjustments to Confirm Acquisition) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Business Acquisition [Line Items]
Total revenues	$ 1,762	$ 2,087
Net earnings (loss)	$ 216	$ (1,815)
Basic net loss per share	$ 0.33	$ (4.82)
Devon and WPX Agreement [Member] | Pro Forma [Member]
Business Acquisition [Line Items]
Total revenues		$ 3,485
Net earnings (loss)		$ (1,864)
Basic net loss per share		$ (2.77)