Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Jan. 07, 2021	Mar. 31, 2021	Mar. 31, 2020
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		$ 195	$ 200
Cash payments for divestitures		10
Barnett Shale [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		$ 185
Devon and WPX Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Date of agreement	Jan. 07, 2021	Jan. 07, 2021
Conversion of common stock into right to recieve per share	$ 0.5165
WPX and Howard Energy Partners [Member]
Summary Of Significant Accounting Policies [Line Items]
Voting interest in the join venture legal entity		50.00%