Goodwill and Other Intangibles - Changes in Goodwill (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Goodwill [Roll Forward]
Balance as of January 1, 2021	$ 579
Goodwill resulted from the acquisition of Direct Energy	1,250
Impairment losses	(35)
Foreign currency translation	1
Balance as of December 31, 2021	1,795
Texas
Goodwill [Roll Forward]
Balance as of January 1, 2021	324
Goodwill resulted from the acquisition of Direct Energy	427
Impairment losses	0
Foreign currency translation	0
Balance as of December 31, 2021	751
East
Goodwill [Roll Forward]
Balance as of January 1, 2021	240
Goodwill resulted from the acquisition of Direct Energy	648
Impairment losses	(35)
Foreign currency translation	0
Balance as of December 31, 2021	853
West/Services/Other
Goodwill [Roll Forward]
Balance as of January 1, 2021	15
Goodwill resulted from the acquisition of Direct Energy	175
Impairment losses	0
Foreign currency translation	1
Balance as of December 31, 2021	$ 191