Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 34,795	$ 34,868
Other comprehensive income (loss), net of income taxes	14	54
Ending balance	23,491	34,313
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(6)	(5)
OCI before reclassifications		0
Amounts reclassified from AOCI	0	0
Other comprehensive income (loss), net of income taxes	0	0
Ending balance	0	(5)
Gains (Losses) on Cash Flow Hedges | Exelon Generation Co L L C [Member]
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	(2,721)	(3,372)
OCI before reclassifications		(2)
Amounts reclassified from AOCI	14	55
Other comprehensive income (loss), net of income taxes	14	53
Ending balance	(713)	(3,319)
Pension and Non-Pension Postretirement Benefit Plan Items | Exelon Generation Co L L C [Member]
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	(23)	(23)
OCI before reclassifications		1
Amounts reclassified from AOCI	0	0
Other comprehensive income (loss), net of income taxes	0	1
Ending balance	0	(22)
Foreign Currency Items | Exelon Generation Co L L C [Member]
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	(2,750)	(3,400)
OCI before reclassifications		(1)
Amounts reclassified from AOCI	14	55
Other comprehensive income (loss), net of income taxes	14	54
Ending balance	(713)	$ (3,346)
Total | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of income taxes	$ 2,023