Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 25,079	$ 25,066	$ 24,744	$ 23,656	$ 23,491	$ 34,795	$ 24,744	$ 34,795
Other comprehensive income (loss), net of income taxes	34	9	(1)	9	12	14	42	35
Ending balance	25,470	25,079	25,066	24,582	23,656	23,491	25,470	24,582
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	17	8	2	0	0	(6)	2	(6)
OCI before reclassifications	22	9	6		0
Amounts reclassified from AOCI	(1)	0	0	0	0	0
Other comprehensive income (loss), net of income taxes	21	9	6	0	0	0
Ending balance	38	17	8	0	0	0	38	0
Gains (Losses) on Cash Flow Hedges | Exelon Generation Co L L C
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of income taxes						6
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(647)	(647)	(640)	(701)	(713)	(2,721)	(640)	(2,721)
OCI before reclassifications	(3)	(3)	(10)		2
Amounts reclassified from AOCI	16	3	3	9	10	14
Other comprehensive income (loss), net of income taxes	13	0	(7)	9	12	14
Ending balance	(634)	(647)	(647)	(692)	(701)	(713)	(634)	(692)
Pension and Non-Pension Postretirement Benefit Plan Items | Exelon Generation Co L L C
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of income taxes						1,994
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	0	0	0	0	0	(23)	0	(23)
OCI before reclassifications	0	0	0		0
Amounts reclassified from AOCI	0	0	0	0	0	0
Other comprehensive income (loss), net of income taxes	0	0	0	0	0	0
Ending balance	0	0	0	0	0	0	0	0
Foreign Currency Items | Exelon Generation Co L L C
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of income taxes						23
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(630)	(639)	(638)	(701)	(713)	(2,750)	(638)	(2,750)
OCI before reclassifications	19	6	(4)		2
Amounts reclassified from AOCI	15	3	3	9	10	14
Other comprehensive income (loss), net of income taxes	34	9	(1)	9	12	14
Ending balance	$ (596)	$ (630)	$ (639)	$ (692)	$ (701)	(713)	$ (596)	$ (692)
Total | Exelon Generation Co L L C
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of income taxes						$ 2,023