Revenue Recognition (Disaggregation of Revenue on Geographic Basis) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,598	$ 527	$ 3,720	$ 1,529
E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	1,179	308	2,616	884
Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	1,165	298	2,574	853
Operating Segments | E&P | Appalachia
Disaggregation of Revenue [Line Items]
Total operating revenues	1,033	297	2,441	852
Operating Segments | E&P | Haynesville
Disaggregation of Revenue [Line Items]
Total operating revenues	132	0	132	0
Operating Segments | E&P | Other
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 0	$ 1	$ 1	$ 1