Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Operations and Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Expenses [Abstract]
Total operating expenses	$ 30,240	$ 30,096	$ 32,143
Operating income (loss)	2,823	4,374	3,891
Other income and (deductions)
Interest expense, net	(1,610)	(1,591)	(1,529)
Other, net	1,145	1,227	(112)
Total other income and (deductions)	(490)	(389)	(1,666)
Income taxes	373	774	118
Net income (loss)	1,954	3,028	2,079
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic cost	(40)	(65)	(66)
Actuarial loss reclassified to periodic cost	190	149	247
Unrealized gain on cash flow hedges	(3)	0	12
Unrealized (loss) gain on foreign currency translation	4	6	(10)
Other comprehensive income (loss)	(206)	(198)	42
Comprehensive Income	1,757	2,737	2,046
Exelon Corporate [Member]
Operating Expenses [Abstract]
Operating and maintenance	(2)	33	(5)
Operating and maintenance from affiliates	10	9	9
Other	2	1	4
Total operating expenses	10	43	8
Operating income (loss)	(10)	(43)	(8)
Other income and (deductions)
Interest expense, net	(378)	(321)	(312)
Equity in earnings (losses) of unconsolidated affiliates	2,313	3,254	2,183
Interest income from affiliates, net	30	39	42
Other, net	15	14	3
Total other income and (deductions)	1,980	2,986	1,916
Income before income taxes	1,970	2,943	1,908
Income taxes	7	7	(97)
Net income (loss)	1,963	2,936	2,005
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic cost	(40)	(64)	(66)
Actuarial loss reclassified to periodic cost	190	148	247
Pension and non-pension postretirement benefit plan valuation adjustment	(357)	(289)	(143)
Unrealized gain on cash flow hedges	(1)	1	12
Unrealized gain (loss) on equity investments	0	0	1
Unrealized (loss) gain on foreign currency translation	0	0	(10)
Other comprehensive income (loss)	(208)	(204)	41
Comprehensive Income	$ 1,755	$ 2,732	$ 2,046