Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 36,347	$ 33,039	$ 34,438
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	4,584	4,645	5,074
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	4,060	4,024	4,293
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	1,575	1,431	1,596
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	1,181	958	1,013
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	4,890	4,002	4,246
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	16,290	15,060	16,222
Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	3,379	2,003	2,210
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(20)	540	492
Unrealized Gain (Loss) on Securities	633	110	(4)
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	19,649	17,603	18,924
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	36,347	33,039	34,438
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	4,564	4,617	5,070
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	4,060	4,029	4,327
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	1,576	1,432	1,596
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	1,172	933	997
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	4,918	4,049	4,295
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	16,290	15,060	16,285
Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	3,379	2,003	2,148
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Securities	565	295	(215)
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	19,649	17,603	18,924
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(3,501)	(3,322)	(3,166)
Revenue from Related Parties	0	4	2
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	20	28	4
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	(5)	(34)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	(1)	(1)	0
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	9	25	16
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	(28)	(47)	(49)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	(63)
Intersegment Eliminations [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	62
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	1
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	0
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(20)	540	491
Contracts with Customers [Member] | Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	4,381	4,785	5,053
Contracts with Customers [Member] | Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	4,265	3,717	4,095
Contracts with Customers [Member] | Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	1,633	1,444	1,571
Contracts with Customers [Member] | Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	896	735	768
Contracts with Customers [Member] | Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	3,937	3,586	3,687
Contracts with Customers [Member] | Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	15,112	14,267	15,174
Contracts with Customers [Member] | Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	1,777	1,283	1,446
Contracts with Customers [Member] | Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	17,254	15,905	17,060
Contracts with Customers [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	365	355	440
Other [Member] | Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	183	(168)	17
Other [Member] | Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	(205)	312	232
Other [Member] | Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(57)	(12)	25
Other [Member] | Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	276	198	229
Other [Member] | Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	981	463	608
Other [Member] | Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	1,178	793	1,111
Other [Member] | Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	1,602	720	702
Other [Member] | Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	2,395	1,698	1,864
Other [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	$ (385)	$ 185	$ 51