Nature of Business (Details) customer in Millions, $ in Millions				12 Months Ended
	Dec. 06, 2021 USD ($) MW	Dec. 01, 2021 USD ($) MW	Jan. 05, 2021 customer state	Dec. 31, 2021 customer MW	Jun. 30, 2021 MW	Jan. 05, 2021 province	Aug. 01, 2019 state
Business Acquisition [Line Items]
Generation capacity (in MW)				18,000
Number of states in which the entity operates | state							9
PJM Coal Generating Assets
Business Acquisition [Line Items]
Generation capacity (in MW)					1,600
East/West Other | Arthur Kill Plant
Business Acquisition [Line Items]
Generation capacity (in MW)	866	866
East/West Other | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Generation capacity (in MW)		4,850
Proceeds from sale of, net of working capital adjustments | $	$ 623	$ 623
Direct Energy
Business Acquisition [Line Items]
Customers served (over) | customer			3
Direct Energy | U.S.
Business Acquisition [Line Items]
Number of states in which the entity operates | state			50
Direct Energy | Canada
Business Acquisition [Line Items]
Provinces in which entity operates			8			8
Home
Business Acquisition [Line Items]
Customers served (over) | customer				6